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# The popular view is that Ozone layer’s depletion-"Tough one"

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Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink]  04 Feb 2013, 11:58
Consider this:

Premise: Socrates is a human
Conclusion: Socrates is intelligent

What is the assumption here for you to reach the conclusion that Socrates is intelligent? The assumption should be Humans are intelligent. So the assumption is based on the premise and the conclusion. It links the two. Any extraneous information should not be considered as assumption because we figure out the assumption based on the argument. For example you cannot say that "Humans who are not beautiful are intelligent and Socrates is not beautiful" is an assumption, though the conclusion would logically follow. This is because the argument doesn't warrant that information.

That is the reason choice D does not fit as an assumption for this question.
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Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink]  04 Feb 2013, 12:31
+1 for D. If we negate this, the conclusion falls apart.
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Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink]  04 Feb 2013, 20:17
Mount Pinatubo in the Philippines spewed forth more than a thousand times the amount of ozone-depleting chemicals in one volcanic eruption than all the fluorocarbons manufactured by wicked, diabolical and insensitive corporations in history.

The passage clearly compares the amount of chemicals released in the eruption with the amount that industries spew.

Clearly the pre-thinking is that the chemicals released during the process has to have the same impact on ozone layer. Only then the comparison is possible.

I was confused between option B and E. I chose B but in retrospect option E sounds better.
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Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink]  05 Feb 2013, 01:39
SravnaTestPrep wrote:
Dinesh2Apr wrote:
E. The rate at which an ozone depleting chemical, whether man-made or released in a volcanic eruption, is released is not more important in the destruction of ozone layer than the quantity of chemicals released. - this option states that rate is not as important as quantity, if we negate this option then it becomes rate is as important as quantity does this break the conclusion ? no, because we do not know whose rate is higher volcano or man made, if man made chemicals rate is higher then the conclusion breaks but if volcanos rate is higher then the conclusion is reinforced because in this situation both the rate and quantity of volcano is higher than man made.

Dear Dinesh2Apr,

It does not matter whether the rate of chemicals released in a volcanic eruption is greater or not. The point is that there is another factor than quantity of chemicals released that may determine how much of ozone is destroyed. Think of it this way. Instead of calling it as rate of release call it as another factor. So the choice would say that there are no other factors than quantity that determines how much of ozone is destroyed. Thus we can see that the author's conclusion would hold absolutely only when quantity is the only factor that determines how much of ozone is destroyed. If there are other factors his argument is not air tight. That is the conclusion would not logically follow from the premise.

Hi,

In my view the argument compares between source of depletion. Not about the quantitiy of depletion.
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Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink]  05 Feb 2013, 17:02
variablechange wrote:
SravnaTestPrep wrote:
Consider this:

Premise: Socrates is a human
Conclusion: Socrates is intelligent

What is the assumption here for you to reach the conclusion that Socrates is intelligent? The assumption should be Humans are intelligent. So the assumption is based on the premise and the conclusion. It links the two. Any extraneous information should not be considered as assumption because we figure out the assumption based on the argument. For example you cannot say that "Humans who are not beautiful are intelligent and Socrates is not beautiful" is an assumption, though the conclusion would logically follow. This is because the argument doesn't warrant that information.

That is the reason choice D does not fit as an assumption for this question.

Dear Sravna,

I have to respectfully disagree with you regarding this question. Your example is based on a sufficient assumption, whereas the question is in relation to a necessary assumption.

I certainly agree with your logic regarding the socrates example. However, that is sufficient as opposed to necessary. Whereas a necessary assumption if we drew in the sufficient assumption that you indicated

Socrates is human.
Socrates is intelligent.
Sufficient asssumption which would make argument stick: "All humans are intelligent" or "All people (people inferred to be human) named Socrates are intelligent"

However, a necessary assumption would be "All Intelligent humans are not named Bob"
This is necessary because if all intelligent humans were named Bob, then the conclusion that Socrates is intelligent couldn't follow.

Dear Variablechange,

My point is we are given the conclusion that socrates is intelligent. From that we can only assume that all humans are intelligent. Similarly, in the question, given the argument, we need to find out the assumption. Whether it be the assumption, strengthen or weaken facts, they should be related to the argument. The assumption question is typically, "which of the following is an assumption on which the argument depends?" In our question how do we know we have to think of the molecular structure of the chemicals being responsible for not reaching the stratosphere, given the argument? So anything not related to the argument is out of scope.
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Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink]  05 Feb 2013, 18:23
Expert's post
variablechange wrote:
SravnaTestPrep wrote:
Consider this:

Premise: Socrates is a human
Conclusion: Socrates is intelligent

What is the assumption here for you to reach the conclusion that Socrates is intelligent? The assumption should be Humans are intelligent. So the assumption is based on the premise and the conclusion. It links the two. Any extraneous information should not be considered as assumption because we figure out the assumption based on the argument. For example you cannot say that "Humans who are not beautiful are intelligent and Socrates is not beautiful" is an assumption, though the conclusion would logically follow. This is because the argument doesn't warrant that information.

That is the reason choice D does not fit as an assumption for this question.

Dear Sravna,

I have to respectfully disagree with you regarding this question. Your example is based on a sufficient assumption, whereas the question is in relation to a necessary assumption.

I certainly agree with your logic regarding the socrates example. However, that is sufficient as opposed to necessary. Whereas a necessary assumption if we drew in the sufficient assumption that you indicated

Socrates is human.
Socrates is intelligent.
Sufficient asssumption which would make argument stick: "All humans are intelligent" or "All people (people inferred to be human) named Socrates are intelligent"

However, a necessary assumption would be "All Intelligent humans are not named Bob"
This is necessary because if all intelligent humans were named Bob, then the conclusion that Socrates is intelligent couldn't follow.

Hi Variablechange,

I would like to give you 10 Kudos for this post. Let me know how can I do this

I must say you have used an extremely relevant yet simple analogy to explain a case, which is difficult to understand in the first place.

This is my first post on the forum after the question and I thought I need to start it by complementing you.BTW, refer to my below post where I mention specific OG examples which have these necessary assumptions as correct answer choices.

Great job

-Chiranjeev
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Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink]  05 Feb 2013, 18:27
Dear Variablechange,

Coming to your point of necessary assumption, the assumption in choice D is not really required. We know from the argument that the quantity of chemicals released determines how much of ozone is depleted. So to make the argument valid all we need to do is to say that there is no factor more important than the quantity of chemicals released in determining ozone depletion. So even without saying D we can make the argument valid.
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Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink]  05 Feb 2013, 18:35
Expert's post
SravnaTestPrep wrote:
The popular view is that Ozone layer’s depletion is real, as certain as Neil Armstrong's landing on the moon. While that may be the case, the attribution of such depletion to man-made chemicals is not true. Mount Pinatubo in the Philippines spewed forth more than a thousand times the amount of ozone-depleting chemicals in one volcanic eruption than all the fluorocarbons manufactured by wicked, diabolical and insensitive corporations in history. Mankind can't possibly equal the output of even one eruption from Pinatubo, much less 4 billion years' worth of them, so how can it be held responsible for destroying ozone.

Which of the following is an assumption on which the argument of the author depends?

A. It would take mankind more than 4 billion years to destroy Ozone. how many years is not the question, but the question is that can mankind be responsible for ozone depletion ?
B. Each molecule of ozone depleting chemical released during an eruption of Mount Pinatubo destroys the same quantity of ozone as a molecule of fluorocarbons. may be less but may be even more
C. The amount of ozone-depleting chemicals released during a single eruption in Mount Pinatubo is much higher than the quantity of fluorocarbons produced by the companies not an assumption, already mentioned in the argument
D. The molecular structure of ozone-depleting chemicals released during a volcanic eruption does not prevent them from reaching the stratosphere, the layer of the atmosphere where the ozone layer resides.
negate this - if the molecules from Volcanic eruptions can't reach the ozone layer, they wont deplete it
E. The rate at which an ozone depleting chemical, whether man-made or released in a volcanic eruption, is released is not more important in the destruction of ozone layer than the quantity of chemicals released. we don't really know whose rate is higher - volcanic eruption or industries

The logic of Choice D that chemicals released in a volcanic eruption may not reach the stratosphere and therefore not destroy ozone is fine but the problem is it is not related to the author's argument. You would want to select a choice that relates to the author's argument and Choice E does that best. This is because the author makes his point by saying that the quantity of chemicals released in a volcanic eruption is enormously more than that released in man-made reactions. So his central assumption is that quantity of chemicals released determines how much of ozone is destroyed. Choice E represents that assumption by saying factors other than quantity released such as the rate of release of chemicals are not important.

Hi SravnaTestPrep,

Let me begin by Thanking you for your contributions to the thread.

Coming to your point, I am not sure how you say that choice D is not related to the author's argument. If choice D doesn't hold, the argument falls apart - what else do we need to make something relevant to the argument?

If the point of contention is that Choice D talks about whether chemicals in a volcanic eruption would be able to reach stratosphere, which has not been discussed in the main argument, then consider the following GMAT Prep question:

Frobisher, a sixteenth-century English explorer, had soil samples from Canada’s Kodlunarn Island examined for gold content. Because high gold content was reported, Elizabeth I funded two mining expeditions. Neither expedition found any gold there. Modern analysis of the island’s soil indicates a very low gold content. Thus the methods used to determine the gold content of Frobisher’s samples must have been inaccurate.

Which of the following is an assumption on which the argument depends?

A. The gold content of the soil on Kodlunarn Island is much lower today than it was in the sixteenth century.
B. The two mining expeditions funded by Elizabeth I did not mine the same part of Kodlunarn Island.
C. The methods used to assess gold content of the soil samples provided by Frobisher were different from those generally used in the sixteenth century.
D. Frobisher did not have soil samples from any other Canadian island examined for gold content.
E. Gold was not added to the soil samples collected by Frobisher before the samples were examined.

Here the correct choice is E. However, as one can see, whether Gold was added to the soil samples or not, has not been discussed or even touched upon in the main argument.

For more examples, you can refer to the below threads (all GMAT Prep questions):
press-secretary-our-critics-claim-that-the-president-s-16458.html
cr-agr-societies-15611.html
the-earth-s-rivers-constantly-carry-dissolved-salts-into-its-65775.html

In all of these examples, the assumption brings in some other point of view - if you negate this, your conclusion will fall apart.

Hope this helps.

Thanks,
Chiranjeev
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Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink]  05 Feb 2013, 18:57
egmat wrote:
SravnaTestPrep wrote:
The popular view is that Ozone layer’s depletion is real, as certain as Neil Armstrong's landing on the moon. While that may be the case, the attribution of such depletion to man-made chemicals is not true. Mount Pinatubo in the Philippines spewed forth more than a thousand times the amount of ozone-depleting chemicals in one volcanic eruption than all the fluorocarbons manufactured by wicked, diabolical and insensitive corporations in history. Mankind can't possibly equal the output of even one eruption from Pinatubo, much less 4 billion years' worth of them, so how can it be held responsible for destroying ozone.

Which of the following is an assumption on which the argument of the author depends?

A. It would take mankind more than 4 billion years to destroy Ozone. how many years is not the question, but the question is that can mankind be responsible for ozone depletion ?
B. Each molecule of ozone depleting chemical released during an eruption of Mount Pinatubo destroys the same quantity of ozone as a molecule of fluorocarbons. may be less but may be even more
C. The amount of ozone-depleting chemicals released during a single eruption in Mount Pinatubo is much higher than the quantity of fluorocarbons produced by the companies not an assumption, already mentioned in the argument
D. The molecular structure of ozone-depleting chemicals released during a volcanic eruption does not prevent them from reaching the stratosphere, the layer of the atmosphere where the ozone layer resides.
negate this - if the molecules from Volcanic eruptions can't reach the ozone layer, they wont deplete it
E. The rate at which an ozone depleting chemical, whether man-made or released in a volcanic eruption, is released is not more important in the destruction of ozone layer than the quantity of chemicals released. we don't really know whose rate is higher - volcanic eruption or industries

The logic of Choice D that chemicals released in a volcanic eruption may not reach the stratosphere and therefore not destroy ozone is fine but the problem is it is not related to the author's argument. You would want to select a choice that relates to the author's argument and Choice E does that best. This is because the author makes his point by saying that the quantity of chemicals released in a volcanic eruption is enormously more than that released in man-made reactions. So his central assumption is that quantity of chemicals released determines how much of ozone is destroyed. Choice E represents that assumption by saying factors other than quantity released such as the rate of release of chemicals are not important.

Hi SravnaTestPrep,

Let me begin by Thanking you for your contributions to the thread.

Coming to your point, I am not sure how you say that choice D is not related to the author's argument. If choice D doesn't hold, the argument falls apart - what else do we need to make something relevant to the argument?

If the point of contention is that Choice D talks about whether chemicals in a volcanic eruption would be able to reach stratosphere, which has not been discussed in the main argument, then consider the following GMAT Prep question:

Frobisher, a sixteenth-century English explorer, had soil samples from Canada’s Kodlunarn Island examined for gold content. Because high gold content was reported, Elizabeth I funded two mining expeditions. Neither expedition found any gold there. Modern analysis of the island’s soil indicates a very low gold content. Thus the methods used to determine the gold content of Frobisher’s samples must have been inaccurate.

Which of the following is an assumption on which the argument depends?

A. The gold content of the soil on Kodlunarn Island is much lower today than it was in the sixteenth century.
B. The two mining expeditions funded by Elizabeth I did not mine the same part of Kodlunarn Island.
C. The methods used to assess gold content of the soil samples provided by Frobisher were different from those generally used in the sixteenth century.
D. Frobisher did not have soil samples from any other Canadian island examined for gold content.
E. Gold was not added to the soil samples collected by Frobisher before the samples were examined.

Here the correct choice is E. However, as one can see, whether Gold was added to the soil samples or not, has not been discussed or even touched upon in the main argument.

For more examples, you can refer to the below threads (all GMAT Prep questions):
press-secretary-our-critics-claim-that-the-president-s-16458.html
cr-agr-societies-15611.html
the-earth-s-rivers-constantly-carry-dissolved-salts-into-its-65775.html

In all of these examples, the assumption brings in some other point of view - if you negate this, your conclusion will fall apart.

Hope this helps.

Thanks,
Chiranjeev

Dear Chiranjeev,

I still stand by my opinion that it is erroneous to make assumptions which are not related to the argument notwithstanding that GMAC uses such questions. The assumption question asks for an assumption on which the argument depends. In the above example it is wrong to say that choice E is the right answer because the argument does not necessarily depend upon choice E. For example the assumption could well have been: "the report of high gold content was not a fabricated one." So a more general assumption is required for this argument.

We do find questions such as these in the GMAT. Therefore the best thing to do would be to fall in line with it.
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Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink]  05 Feb 2013, 19:35
Premise 1: Quantity of chemicals released determines how much of ozone is depleted
Premise 2: Volcanic eruptions have released more chemicals
Conclusion: Volcanic eruptions have depleted more ozone.

To the above add the following premise

Premise 3: Rate of release of chemicals is more important in determining the amount of ozone depleted

Now given the above premise can we reach the conclusion stated above? I guess not. Because unless we know certainly what premise 3 would ensue we cannot the the conclusion stated. That is my point.
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Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink]  05 Feb 2013, 20:21
Expert's post
SravnaTestPrep wrote:
Premise 1: Quantity of chemicals released determines how much of ozone is depleted

There is the problem.

"Quantity of chemicals released determines how much of ozone is depleted." is not a premise. It is what the author is implying/assuming. It is not given as a fact.

Let's review the argument:

The popular view is that Ozone layer’s depletion is real, as certain as Neil Armstrong's landing on the moon. - A fact about what people generally think.

While that may be the case, the attribution of such depletion to man-made chemicals is not true. - Conclusion of the argument

Mount Pinatubo in the Philippines spewed forth more than a thousand times the amount of ozone-depleting chemicals in one volcanic eruption than all mankind in history. - Fact about who produces more ozone-depleting chemicals

The argument does not tell us that "Quantity of chemicals released determines how much of ozone is depleted." It is something the author is implying. He is assuming that if more chemicals are released, more ozone is depleted. The point is that if the 'chemicals released' are unable to reach the ozone layer, they cannot deplete it. So the author is assuming that the chemicals released are able to reach the ozone layer.

Hence answer has to be (D).
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Get started with Veritas Prep GMAT On Demand for $199 Veritas Prep Reviews Intern Joined: 15 Aug 2012 Posts: 47 Followers: 1 Kudos [?]: 23 [0], given: 2 Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink] 05 Feb 2013, 20:44 egmat wrote: Dinesh2Apr wrote: Conclusion :- Ozone Depleting chemicals from volcano eruptions have depleted the ozone layer more than man made ozone depleting chemicals because the quantity of chemicals from volcano is more than man made chemicals Assumption :- even if the quantity is more, the chemicals from volcano should actually cause the depletion A. It would take mankind more than 4 billion years to destroy Ozone. - OFS, from the given premise the quantity of man made chemicals will always be lower than natural chemicals B. Each molecule of ozone depleting chemical released during an eruption of Mount Pinatubo destroys the same quantity of ozone as a molecule of fluorocarbons. - OFS the amount of ozone destroyed by a single amount is not the scope of passage C. The amount of ozone-depleting chemicals released during a single eruption in Mount Pinatubo is much higher than the quantity of fluorocarbons produced by the companies - already stated in the passage, and our scope is total quantity not only 1 eruption D. The molecular structure of ozone-depleting chemicals released during a volcanic eruption does not prevent them from reaching the stratosphere, the layer of the atmosphere where the ozone layer resides. - Correct, if for some reason the chemical from volcano does not reach the ozone layer then chemical from volcano cannot be the cause of ozone depletion. E. The rate at which an ozone depleting chemical, whether man-made or released in a volcanic eruption, is released is not more important in the destruction of ozone layer than the quantity of chemicals released. - this option states that rate is not as important as quantity, if we negate this option then it becomes rate is as important as quantity does this break the conclusion ? no, because we do not know whose rate is higher volcano or man made, if man made chemicals rate is higher then the conclusion breaks but if volcanos rate is higher then the conclusion is reinforced because in this situation both the rate and quantity of volcano is higher than man made. IMO :- D Hi Dinesh, Your answer is correct. Choice D is the answer. However, I think your explanations for rejecting other options are not always correct. Dinesh2Apr wrote: B. Each molecule of ozone depleting chemical released during an eruption of Mount Pinatubo destroys the same quantity of ozone as a molecule of fluorocarbons. - OFS the amount of ozone destroyed by a single amount is not the scope of passage If amount destroyed by single molecule is out of scope, how come molecular structure discussed in Choice D is within the scope? Dinesh2Apr wrote: E. The rate at which an ozone depleting chemical, whether man-made or released in a volcanic eruption, is released is not more important in the destruction of ozone layer than the quantity of chemicals released. - this option states that rate is not as important as quantity, if we negate this option then it becomes rate is as important as quantity does this break the conclusion ? no, because we do not know whose rate is higher volcano or man made, if man made chemicals rate is higher then the conclusion breaks but if volcanos rate is higher then the conclusion is reinforced because in this situation both the rate and quantity of volcano is higher than man made. The option states that rate is "not more important" than quantity - not "not as important" as quantity. So, if we negate this, we get that either rate is more important than quantity. Then, you correctly say that we don't know whose rate is higher. But an important point here is that even if rate of man-made chemical is higher than that of volcanic eruption, the conclusion won't break apart. Why? Simply because we don't know a direct relation between rate of eruption to the depletion. If you think that that is obvious, then revisit Option D. Negation of Option D breaks down the link between quantity of chemicals produced to their impact on the ozone layer. While chemicals released in volcanic eruption might be higher, if Option D is not true, these chemicals impact the ozone layer. Even though you chose the right choice, the idea is that you understand these nuances so that when you see other OG question, you are more sure while selecting and rejecting option statements. Hope this helps Thanks, Chiranjeev Hi Chiranjeev, I do see the shortcomings in the reasoning for eliminating incorrect answers, thanks for the detailed analysis. Senior Manager Joined: 17 Dec 2012 Posts: 395 Location: India Followers: 20 Kudos [?]: 259 [0], given: 10 Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink] 05 Feb 2013, 20:51 VeritasPrepKarishma wrote: SravnaTestPrep wrote: Premise 1: Quantity of chemicals released determines how much of ozone is depleted There is the problem. "Quantity of chemicals released determines how much of ozone is depleted." is not a premise. It is what the author is implying/assuming. It is not given as a fact. . Dear VeritasPrepKarishma, How can it be not the premise? It is the author's view that the quantity of chemicals released determines how much of ozone is depleted. And he makes his conclusion solely based on that view. What else is the premise of the argument then? _________________ Srinivasan Vaidyaraman Sravna Test Prep http://www.sravna.com Classroom Courses in Chennai Free Online Material Veritas Prep GMAT Instructor Joined: 16 Oct 2010 Posts: 5735 Location: Pune, India Followers: 1444 Kudos [?]: 7567 [0], given: 186 Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink] 05 Feb 2013, 21:06 Expert's post SravnaTestPrep wrote: Dear VeritasPrepKarishma, How can it be not the premise? It is the author's view that the quantity of chemicals released determines how much of ozone is depleted. And he makes his conclusion solely based on that view. What else is the premise of the argument then? As you said, it is the author's view. Views/opinions are not premises. Premises are only the facts given. The given premises are: - The popular view is that Ozone layer’s depletion is real, as certain as Neil Armstrong's landing on the moon. - The fact is that this is a popular view among people. - Mount Pinatubo in the Philippines spewed forth more than a thousand times the amount of ozone-depleting chemicals in one volcanic eruption than all the fluorocarbons manufactured by wicked, diabolical and insensitive corporations in history. - This is a fact that Mount Pinatubo spews more ozone depleting chemicals that man. - Mankind can't possibly equal the output of even one eruption from Pinatubo, much less 4 billion years' worth of them - Again, a fact about chemical output. No other fact/premise is given. _________________ Karishma Veritas Prep | GMAT Instructor My Blog Get started with Veritas Prep GMAT On Demand for$199

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Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink]  05 Feb 2013, 21:11
VeritasPrepKarishma wrote:
SravnaTestPrep wrote:

Dear VeritasPrepKarishma,

How can it be not the premise? It is the author's view that the quantity of chemicals released determines how much of ozone is depleted. And he makes his conclusion solely based on that view. What else is the premise of the argument then?

As you said, it is the author's view. Views/opinions are not premises. Premises are only the facts given.

The given premises are:

- The popular view is that Ozone layer’s depletion is real, as certain as Neil Armstrong's landing on the moon. - The fact is that this is a popular view among people.
- Mount Pinatubo in the Philippines spewed forth more than a thousand times the amount of ozone-depleting chemicals in one volcanic eruption than all the fluorocarbons manufactured by wicked, diabolical and insensitive corporations in history. - This is a fact that Mount Pinatubo spews more ozone depleting chemicals that man.
- Mankind can't possibly equal the output of even one eruption from Pinatubo, much less 4 billion years' worth of them - Again, a fact about chemical output.

No other fact/premise is given.

Premise need not be a fact alone. It can be a proposition or in other words a view. The important point that is the conclusion of the argument should be based on that. In our case the conclusion of the author is based on his view that quantity of chemicals released is what is important.
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Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink]  06 Feb 2013, 01:36
Finally, I am relaxed now.......
Its not that my answer is correct so i am relaxed....but i understood why an answer, which was a close call is wrong, that makes me happy.

Thanks a trillion to Cheeranjeev.....................
Pls continue the work of posting but do not delay in posting the answer, i cannot explain i was not able to sleep........
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Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink]  07 Feb 2013, 03:56
D should be the answer. It can be tested by negation test as already explained.

On the other hand, if we can relate the amount with molecules, then A should also be considered.
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Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink]  12 Feb 2013, 22:50
Expert's post
Here's the official answer and explanation:

Understanding the passage

Conclusion:
The attribution of depletion of Ozone layer to man-made chemicals is not true.

Premises:
1. Mount Pinatubo in the Philippines spewed forth more than a thousand times the amount of ozone-depleting chemicals in one volcanic eruption than all the fluorocarbons manufactured by wicked, diabolical and insensitive corporations in history
2. Mankind can't possibly equal the output of even one eruption from Pinatubo, much less 4 billion years' worth of them

In this case, premises 1 and 2 are set of dependent information pieces and comprise a single reason used by the author to arrive at the conclusion. In essence, the reason is:

Ozone depleting chemicals produced by Mount Pinatubo is much greater (probably billion of times) than ozone depleting chemicals (fluorocarbons) produced by mankind.
This reason is used to signal that man-made chemicals can only play an insignificant role in the depletion of Ozone layer.
Therefore, (Conclusion) Man-made chemicals can’t be held responsible for ozone layer depletion.

Prethinking

As we can see, the argument is talking only in terms of the amount of ODC ( Ozone Depleting Chemicals), not in terms of their impact on the ozone layer. This is a missing link that is needed to establish the correctness of the argument.
So, a statement like “ODCs generated by volcanic eruptions have the same effect on the Ozone as ODCs generated by mankind”, would complete the argument.
However, this is not a must-be-true statement. Why? Because we know that the quantity of volcanic ODCs is probably billions of times greater than man-made ODCs, therefore, even if volcanic ODCs have much less effect than man-made ODCs, our conclusion would still hold.

Therefore, our only requirement can be that volcanic ODCs have at least some effect on the Ozone layer.
However, why would ODCs be called so if they don’t have any effect on Ozone layer. So, they have to have some impact. This leads me to think that there are only two situations in which the argument won't hold:

1. Volcanic ODCs don’t reach Ozone layer due to some reason (hypothetical) –
a. Probably because due to their high temperature. they react with some chemical as soon as they reach atmosphere and this reaction snaps their ability to deplete Ozone layer
b. Their chemical or physical properties is different from man-made ODCs and these properties prevent them from reaching Ozone layer

2. Volcanic ODCs can’t deplete unless the depletion has been started by man-made ODCs. Suppose, Ozone layer exists in a very stable state – this state cannot be affected by volcanic ODCs. However, once man-made ODCs can start reactions with this stable state of Ozone and deplete it, this makes the Ozone layer reactive even to Volcanic ODCs.

In both the situations above, our conclusion won’t hold. Therefore, negation of either of the two statements could be a valid assumption and therefore, answer to our question.

A. It would take mankind more than 4 billion years to destroy Ozone. – So what? We are concerned with the cause of depletion, not the time-frame. Incorrect.

B. Each molecule of ozone depleting chemical released during an eruption of Mount Pinatubo destroys the same quantity of ozone as a molecule of fluorocarbons. – As we analyzed in the pre-thinking, this is not required. Even if a molecule of volcanic chemical destroys much less ozone than a man-made chemical, the conclusion will still hold. Therefore, this is not a must be true statement. Thus, Incorrect.

C. The amount of ozone-depleting chemicals released during a single eruption in Mount Pinatubo is much higher than the quantity of fluorocarbons produced by the companies – This can be inferred from the passage. Therefore, this presents no new information and thus, cannot be an assumption. Incorrect.

D. The molecular structure of ozone-depleting chemicals released during a volcanic eruption does not prevent them from reaching the stratosphere, the layer of the atmosphere where the ozone layer resides. – This is in line with our prethinking. If these volcanic ODCs don’t reach ozone layer, then the reasoning of the argument breaks down. Therefore, this is a must-be-true statement for the argument to hold. Correct.

E. The rate at which an ozone depleting chemical, whether man-made or released in a volcanic eruption, is released is not more important in the destruction of ozone layer than the quantity of chemicals released. – Given this statement is in a negative form “not more”. Let’s negate it and see if the conclusion breaks down. We can see that even if rate is more important than the quantity, it doesn’t impact the conclusion, since we don’t know whether slow rate depletes Ozone layer more or fast rate depletes more. Therefore, Incorrect.

Therefore, the answer choice is Option D.

Hope this helps

-Chiranjeev Singh
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Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink]  13 Feb 2013, 19:10
egmat wrote:
Here's the official answer and explanation:

Understanding the passage

Conclusion:
The attribution of depletion of Ozone layer to man-made chemicals is not true.

Premises:
1. Mount Pinatubo in the Philippines spewed forth more than a thousand times the amount of ozone-depleting chemicals in one volcanic eruption than all the fluorocarbons manufactured by wicked, diabolical and insensitive corporations in history
2. Mankind can't possibly equal the output of even one eruption from Pinatubo, much less 4 billion years' worth of them

In this case, premises 1 and 2 are set of dependent information pieces and comprise a single reason used by the author to arrive at the conclusion. In essence, the reason is:

Ozone depleting chemicals produced by Mount Pinatubo is much greater (probably billion of times) than ozone depleting chemicals (fluorocarbons) produced by mankind.
This reason is used to signal that man-made chemicals can only play an insignificant role in the depletion of Ozone layer.
Therefore, (Conclusion) Man-made chemicals can’t be held responsible for ozone layer depletion.

Prethinking

As we can see, the argument is talking only in terms of the amount of ODC ( Ozone Depleting Chemicals), not in terms of their impact on the ozone layer. This is a missing link that is needed to establish the correctness of the argument.
So, a statement like “ODCs generated by volcanic eruptions have the same effect on the Ozone as ODCs generated by mankind”, would complete the argument.
However, this is not a must-be-true statement. Why? Because we know that the quantity of volcanic ODCs is probably billions of times greater than man-made ODCs, therefore, even if volcanic ODCs have much less effect than man-made ODCs, our conclusion would still hold.

Therefore, our only requirement can be that volcanic ODCs have at least some effect on the Ozone layer.
However, why would ODCs be called so if they don’t have any effect on Ozone layer. So, they have to have some impact. This leads me to think that there are only two situations in which the argument won't hold:

1. Volcanic ODCs don’t reach Ozone layer due to some reason (hypothetical) –
a. Probably because due to their high temperature. they react with some chemical as soon as they reach atmosphere and this reaction snaps their ability to deplete Ozone layer
b. Their chemical or physical properties is different from man-made ODCs and these properties prevent them from reaching Ozone layer

2. Volcanic ODCs can’t deplete unless the depletion has been started by man-made ODCs. Suppose, Ozone layer exists in a very stable state – this state cannot be affected by volcanic ODCs. However, once man-made ODCs can start reactions with this stable state of Ozone and deplete it, this makes the Ozone layer reactive even to Volcanic ODCs.

In both the situations above, our conclusion won’t hold. Therefore, negation of either of the two statements could be a valid assumption and therefore, answer to our question.

A. It would take mankind more than 4 billion years to destroy Ozone. – So what? We are concerned with the cause of depletion, not the time-frame. Incorrect.

B. Each molecule of ozone depleting chemical released during an eruption of Mount Pinatubo destroys the same quantity of ozone as a molecule of fluorocarbons. – As we analyzed in the pre-thinking, this is not required. Even if a molecule of volcanic chemical destroys much less ozone than a man-made chemical, the conclusion will still hold. Therefore, this is not a must be true statement. Thus, Incorrect.

C. The amount of ozone-depleting chemicals released during a single eruption in Mount Pinatubo is much higher than the quantity of fluorocarbons produced by the companies – This can be inferred from the passage. Therefore, this presents no new information and thus, cannot be an assumption. Incorrect.

D. The molecular structure of ozone-depleting chemicals released during a volcanic eruption does not prevent them from reaching the stratosphere, the layer of the atmosphere where the ozone layer resides. – This is in line with our prethinking. If these volcanic ODCs don’t reach ozone layer, then the reasoning of the argument breaks down. Therefore, this is a must-be-true statement for the argument to hold. Correct.

E. The rate at which an ozone depleting chemical, whether man-made or released in a volcanic eruption, is released is not more important in the destruction of ozone layer than the quantity of chemicals released. – Given this statement is in a negative form “not more”. Let’s negate it and see if the conclusion breaks down. We can see that even if rate is more important than the quantity, it doesn’t impact the conclusion, since we don’t know whether slow rate depletes Ozone layer more or fast rate depletes more. Therefore, Incorrect.

Therefore, the answer choice is Option D.

Hope this helps

-Chiranjeev Singh

In my opinion an assumption should relate to the argument. Only then it makes sense. If we can assume choice D then we can equally assume the following: "Scientists who have the capability of preventing ozone depleting chemicals from reaching the stratosphere would not do so". But does it make sense considering the argument?

The way we need to go about it is that we first take the premise of the argument which is: the quantity of the ozone depleting chemicals determines how much of ozone is depleted. An assumption should be something which fills the gap which the above premise leaves open so that the conclusion is valid. What does the premise miss? It misses the possibility that some other factor than quantity might also determine ozone depletion and it might be more important. So we look for a choice that says exactly that. Choice E does that. I would have been perfect if Choice E had been more general but it does a better job than choice D.

So in spite of the official answer being announced as D, I would still stick with choice E.
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Re: The popular view is that Ozone layer’s depletion-"Tough one" [#permalink]  09 May 2013, 14:58
carcass wrote:

Thanks

Hey Guyys,

The official answer is D . Here is a link to it on beat the GMAT . - http://www.beatthegmat.com/an-assumptio ... 71004.html
People should be made to post the answer along with the question , for the benefit of others using the forum. Question without an answer is as good as no question.
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Re: The popular view is that Ozone layer’s depletion-"Tough one"   [#permalink] 09 May 2013, 14:58

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