Scientists analyzing air bubbles that had been trapped in : GMAT Critical Reasoning (CR)
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# Scientists analyzing air bubbles that had been trapped in

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08 Dec 2009, 10:39
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Scientists analyzing air bubbles that had been trapped in Antarctic ice during the Earth’s last ice age found that the ice-age atmosphere had contained unusually large amounts of ferrous material and surprisingly small amounts of carbon dioxide. One scientist noted that algae absorb carbon dioxide from the atmosphere. The scientist hypothesized that the ferrous material, which was contained in atmospheric dust, had promoted a great increase in the population of Antarctica algae such as diatoms.

Which one of the following, if true, would most seriously undermine the scientist’s hypothesis?

A) Diatoms are a microscopic form of algae that has remained largely unchanged since the last ice age.

(B) Computer models suggest that a large increase in ferrous material today could greatly promote the growth of oceanic algae.

(C) The dust found in the air bubbles trapped in Antarctica ice contained other minerals in addition to the ferrous material.

(D) Sediment from the ocean floor near Antarctica reflects no increase, during the last ice age, in the rate at which the shells that diatoms leave when they die accumulated.

(E) Algae that currently grow in the oceans near Antarctica do not appear to be harmed by even a large increase in exposure to ferrous material.
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Re: Scientists analyzing air bubbles [#permalink]

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10 Jun 2011, 10:29
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vaibhav87 wrote:
Scientists analyzing air bubbles that had been trapped in Antarctic ice during the Earth’s last ice age found that the ice-age atmosphere had contained unusually large amounts of ferrous material and surprisingly small amounts of carbon dioxide. One scientist noted that algae absorb carbon dioxide from the atmosphere. The scientist hypothesized that the ferrous material, which was contained in atmospheric dust, had promoted a great increase in the population of Antarctica algae such as diatoms.

Bubble revealed that air in ice-age had high ferrous content and very little carbon-dioxide.
Hypothesis: Ferrous material increased algae, which in turn absorbed CO2 from atmosphere. This theory explains a possible reason for low CO2 level.

Which one of the following, if true, would most seriously undermine the scientist’s hypothesis?
We need to weaken the hypothesis or prove it wrong.

A) Diatoms are a microscopic form of algae that has remained largely unchanged since the last ice age.
This information actually helps to a certain extent in corroborating the hypothesis. Since Diatoms didn't change much, it still traps CO2 as it during the ice age. Thus, at least the information about the CO2 trapping property of diatoms is not baseless. However, this statement doesn't undermine the hypothesis. It is more like a standalone fact.

(B) Computer models suggest that a large increase in ferrous material today could greatly promote the growth of oceanic algae.
Something true today may not have been true in the past, esp. in ice age when temperature was extreme. Furthermore, this only strengthens the hypothesis that ferrous material might have caused the increase in algae.

(C) The dust found in the air bubbles trapped in Antarctica ice contained other minerals in addition to the ferrous material.
This is additional information that was not a part of the premise. May be it contained sulfur, zinc, aluminum; who cares if it did. So far it carried ferrous materials, the scientists' hypothesis holds good. If the statement said, "the bubble contained other minerals that neutralized the inherent properties of ferrous materials", then it could be a weakening statement. If we assume that these gases may have caused the algae, then we are assuming too much.

(D) Sediment from the ocean floor near Antarctica reflects no increase, during the last ice age, in the rate at which the shells that diatoms leave when they die accumulated.

This statement may not be best in this world to weaken this hypothesis, but certainly is the best of the lot. It is attacking the hypothesis by finding out the fact that the algae's population didn't increase during the ice-age. Thus, the scientists hypothesis that increased population of algae caused the CO2 reduction is questionable.

Now, the scientists may come with a counter-argument that the tests used to actually analyze the sediment are rarely show correct results. Thus, despite your findings from the analysis of the sediments prove that the algae population didn't increase, it actually increased because your test findings are baseless.

Since we have to accept the statement as true, this directly casts a doubt on author's hypothesis.

It would be irrational to assume that the diatoms didn't die. If they didn't die, then they must still be present on the sea surface, making it easier for the scientists to hypothesize.

Correct.

(E) Algae that currently grow in the oceans near Antarctica do not appear to be harmed by even a large increase in exposure to ferrous material.
Who said so that it would be harmed. Scientists said that the algae flourish in ferrous rich atmosphere. Strengthens part of the hypothesis.

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Re: Scientists analyzing air bubbles [#permalink]

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08 Dec 2009, 13:57
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If the scientists did not find an increase in the number of shells that diatoms leave when they die, then clearly there was no increase in the algae and thus the scientists' hypothesis that the ferrous material in the atmosphere was responsible for the increase in algae is wrong!
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Re: Scientists analyzing air bubbles [#permalink]

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09 Dec 2009, 13:24
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C can't be the answer as the passage doesn't mention the impact of other minerals anywhere.
'D' is the best choice since it mentions that there was no significant increase in algae population, hence no reason to believe that it could be the reason for low concentrations of CO2.

IMO D.
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Re: Scientists analyzing air bubbles [#permalink]

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17 Dec 2009, 20:32
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vaibhav87 wrote:
Scientists analyzing air bubbles that had been trapped in Antarctic ice during the Earth’s last ice age found that the ice-age atmosphere had contained unusually large amounts of ferrous material and surprisingly small amounts of carbon dioxide. One scientist noted that algae absorb carbon dioxide from the atmosphere. The scientist hypothesized that the ferrous material, which was contained in atmospheric dust, had promoted a great increase in the population of Antarctica algae such as diatoms.

Which one of the following, if true, would most seriously undermine the scientist’s hypothesis?
Brief: lots of ferrous material,BUT little CO2. Algae absorbs CO2. Conclusion: Scientist hypothesizes FM--> great increase in Algae.
A) Diatoms are a microscopic form of algae that has remained largely unchanged since the last ice age --> even though the diatoms are one type of artarctica algae, however, it is hard to strongly weaken the conclusion because it is just one kind of Algae. I consider this negligible weakening.
(B) Computer models suggest that a large increase in ferrous material today could greatly promote the growth of oceanic algae. -->strengthen
(C) The dust found in the air bubbles trapped in Antarctica ice contained other minerals in addition to the ferrous material. -->other minerals is out of scope.
(D) Sediment from the ocean floor near Antarctica reflects no increase, during the last ice age, in the rate at which the shells that diatoms leave when they die accumulated. --> this suggests that there is no evidence that there are increase in shells which was died diatoms. So, no increase in diatoms. weaken. CORRECT
(E) Algae that currently grow in the oceans near ntarctica do not appear to be harmed by even a large increase in exposure to ferrous material. -->lightly strengthen

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Re: Scientists analyzing air bubbles [#permalink]

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10 Jun 2011, 08:54
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Although i understand D, I don't understand how to take out C.

The question says "if true" which means if you take the statements in the options to be true would it "most seriously" undermine the hypothesis.

How can C be out of scope or Irrelevant when the question itself brings it into scope when you view the argument and the option C as whole? The Scientist hypothesize that the ferrous material in the dust promoted the increase. If you get other minerals into the picture doesn't that question the hypothesis?

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11 Jun 2013, 16:54
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vaibhav87 wrote:
(C) The dust found in the air bubbles trapped in Antarctica ice contained other minerals in addition to the ferrous material.

(D) Sediment from the ocean floor near Antarctica reflects no increase, during the last ice age, in the rate at which the shells that diatoms leave when they die accumulated.

Here's my take on these two:
C) There are a few materials; we hypothesize that ferrous material is the cause.
D) There has been a decrease in death, and thus there has unlikely been an increase in life.

"The scientist hypothesized that the ferrous material, which was contained in atmospheric dust, had promoted a great increase in the population of Antarctica algae such as diatoms"

For (C) to be correct, we are attacking the "ferrous material was the cause" issue.
For (D) to be correct, we are attacking the "increase in population" issue.

In my opinion, for those who say C is correct, you are in a way assuming that there was a - great increase - in the population, but that ferrous material was not the cause.

D is the correct answer because there could not have been a - great increase - in population with absolutely no change in mortality rate.
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Re: Scientists analyzing air bubbles [#permalink]

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08 Dec 2009, 11:17
vaibhav87 wrote:
Scientists analyzing air bubbles that had been trapped in Antarctic ice during the Earth’s last ice age found that the ice-age atmosphere had contained unusually large amounts of ferrous material and surprisingly small amounts of carbon dioxide. One scientist noted that algae absorb carbon dioxide from the atmosphere. The scientist hypothesized that the ferrous material, which was contained in atmospheric dust, had promoted a great increase in the population of Antarctica algae such as diatoms.

Which one of the following, if true, would most seriously undermine the scientist’s hypothesis?

A) Diatoms are a microscopic form of algae that has remained largely unchanged since the last ice age.

(B) Computer models suggest that a large increase in ferrous material today could greatly promote the growth of oceanic algae.

(C) The dust found in the air bubbles trapped in Antarctica ice contained other minerals in addition to the ferrous material.
This option says - not ferrous but some other mineral may have promoted a great increase in the population of algae.
(D) Sediment from the ocean floor near Antarctica reflects no increase, during the last ice age, in the rate at which the shells that diatoms leave when they die accumulated.

(E) Algae that currently grow in the oceans near Antarctica do not appear to be harmed by even a large increase in exposure to ferrous material.

'c'
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Re: Scientists analyzing air bubbles [#permalink]

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08 Dec 2009, 11:35
C is the best Answer. What is the OA?
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Re: Scientists analyzing air bubbles [#permalink]

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09 Dec 2009, 00:02
D it is
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Re: Scientists analyzing air bubbles [#permalink]

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09 Dec 2009, 12:34
Narrowed it down to C or D. Probably would choose D.
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10 Dec 2009, 10:34
OA D
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Re: Scientists analyzing air bubbles [#permalink]

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18 Dec 2009, 12:31
I think the answer is A.

The premises -
1) Large amounts of Ferrous materials found
2) Very little CO2 found
3) Algae absorb CO2

Conclusion
Ferrous materials caused an increase in Algae growth (There is no conclusive evidence to this).
The conclusion would be true if we knew either of the 2
A) Ferrous materials promote algae growth
B) The algae did increase in number thereby reducing the CO2 levels.

Now let us look at the choices
A) Diatoms are a microscopic form of algae that has remained largely unchanged since the last ice age.
This statement negates Statement B above could be true.
(B) Computer models suggest that a large increase in ferrous material today could greatly promote the growth of oceanic algae.
Affirms statement A (incorrect).
(C) The dust found in the air bubbles trapped in Antarctica ice contained other minerals in addition to the ferrous material.
Irrelevant
(D) Sediment from the ocean floor near Antarctica reflects no increase, during the last ice age, in the rate at which the shells that diatoms leave when they die accumulated.
Tempting choice as it might negate statement B, but if the amount of algea did increase it might also increase their lifespan thus not necessarily increasing their death rate. Since this doesn't directly negate statement B and we already have a choice (1) which directly negates it, we can safely assume it's incorrect.
(E) Algae that currently grow in the oceans near Antarctica do not appear to be harmed by even a large increase in exposure to ferrous material.
Indirectly supports statement A.
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Re: Scientists analyzing air bubbles [#permalink]

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19 Dec 2009, 10:09
I agree with above post....number of dead algae didn't increase doesn't mean, number of algae didn't increase.

I feel 'A' is right answer-Diatoms are a microscopic form of algae that has remained largely unchanged since the last ice age - as it clearly (dis)agrees with the hypothesis -"...had promoted a great increase in the population of Antarctica algae such as diatoms."
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Re: Scientists analyzing air bubbles [#permalink]

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15 May 2011, 05:17
D by POE here.
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08 Jun 2011, 23:06
I'm with C. Need explanation why D
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13 Jul 2011, 07:12
I also picked C, which is wrong.

I found D to be assuming too much as well. FM --> large algae population and then algae died (this is fine and can be assumed) but that they must be detectable after several thousand years as a proof that they exist seems a bit much. I think its on the border and by POE I should have got this.
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Re: Scientists analyzing air bubbles [#permalink]

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18 Jul 2011, 20:23
I was tied down between C and D as well. I chose C. But I learnt an important lesson from this example. When you are given new information on a CR problem. You shouldn't assume too much into the new information.

D attacks the conclusion
C attempts to bring a new premise (which is what weakening questions are supposed to do) but doesnt really tie it to the premise.

Great explanation by fluke!
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Re: Scientists analyzing air bubbles [#permalink]

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19 Jul 2011, 03:26
i chose D by POE..
Why not C?
(C) The dust found in the air bubbles trapped in Antarctica ice contained other minerals in addition to the ferrous material.
The chances that ferrous material is still causing the effect still hold good merely because of its presence. even though other minerals are present, they might not be cause of the end result
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Re: Scientists analyzing air bubbles [#permalink]

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20 Jul 2011, 04:46
Chose D
Re: Scientists analyzing air bubbles   [#permalink] 20 Jul 2011, 04:46

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