Scientists analyzing air bubbles that had been trapped in Antarctic ic

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.

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?

Please help clarify this.
Thanks.

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.
talks about diatoms(population has remained unchanged) in general, not specifically about Antarctica region.
(B) Computer models suggest that a large increase in ferrous material today could greatly promote the growth of oceanic algae.
Incorrect - Strengthens the argument
(C) The dust found in the air bubbles trapped in Antarctica ice contained other minerals in addition to the ferrous material.
The statement mentions that air bubbles contained other minerals but if other minerals caused increase in algae population is assuming too much for me. what if they were harmful...
(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.
specifically talks about diatoms population around Antarctica region. 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.
neutral or a weak strengthner because it says ferrous material is not harmful to algae population.

Answer D according to me.

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.

Summary: Scientists found that the atmosphere during the last ice age had large amounts of ferrous material and very less carbon dioxide. Explanation for very less carbon dioxide was that algae absorbed it.
Hypothesis: The increase in algae was because of the ferrous material.

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

Thought process: How can we weaken the Hypothesis?
Either we say the cause of the increase was not ferrous material, or we say there was no increase in algae whatsoever!
"No-increase-whatsoever" gives a lethal blow to the hypothesis!

A) Diatoms are a microscopic form of algae that has remained largely unchanged since the last ice age.
Talks about Diatoms, but not about "no increase whatsoever"

(B) Computer models suggest that a large increase in ferrous material today could greatly promote the growth of oceanic algae.
Says there was "definitely an increase!", thereby strengthening the argument.

(C) The dust found in the air bubbles trapped in Antarctica ice contained other minerals in addition to the ferrous material.
Talks about "other minerals". This does not imply "other minerals caused the increase in algae." Close, but definitely not convincing enough to destroy the hypothesis

(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.
No increase in the mortal remains of algae! No increase in algae whatsoever! This is surely the answer

(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.
Talks about algae of today and not about algae during the last Ice Age.

So answer according to me is D.

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.

Bumping for further discussion

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.

Their are ways to negate a conclusion
1-causal reversal; i:e A DIDNOT MAKE B HAPPEN AND B TOOK TO A HAPPEN
2-A HAPPENED BUT B NEVER HAPPENED
3-A DIDNT HAPPEN BUT B HAPPEN
4-IT IS NOT A RATHER C MADE A TO HAPPEN B

By reading the choices option-D talks when The algae die it accumulates shells, which rate of increase never happen.that means algae dying rate is not increasing since ice age ended, however qn hypothesis says algae population is increasing by ferrous material.now can it be possible that algae population is increasing and not dying atall. its is beyond or contradicting hypothesis by
A(ferrous material) happens but never leads B(algae population).

The qn is we never find time to analys such way under timing pressure
so lets go to the option for elimination.
A-IT TALKS ABOUT ALGAE FORMS,NOT RELEVANT
B-IT IS STRENGTHENING
C-IT GIVES CLUES BUT NOT IMPACTING THE EFFECT OF THE OTHER MATERIAL'S,THE VERY CAUSE WE THING MIGHT PROMOTE.
D-CORRECT
E-ITS TALKING ABOUT EFFECT OF INCREASING ALGAE POPULATION INCREASE.

AFTER ALL WE HAVE TO NEGATE THAT FERROUS MATERIAL CAUSING INCREMENT IN ALGAE POPULATION.

I have a doubt the question says algae 'such as' diatoms so cant we eliminate D on the basis that we might not have diatoms but there is a possibility of other algae ?? I opted for C can someone explain why is D a better choice?

C neither weakens nor strengthens the Conclusion. It just says that Air bubbles contain other elements too. Reason for population growth may be ferrous or may not be ferrous.
Option D on the other hand, says that no increase in the remains of diatoms. Yes the author is providing an example, but a faulty one. So indeed, D is correct.

Posted from my mobile device

Between C and D:

C tells us that the dust found in the air bubbles trapped in Antarctica ice contained other minerals in addition to the ferrous material. But does this actually undermine the scientist's hypothesis? We don't know whether these other minerals had any impact at all on the ferrous material. Without making further assumptions, this choice doesn't tell us much.

D tells us that 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.

If the rate of shells did not increase, we have reason to believe that the population of diatoms did not increase during the last ice age. This isn't iron clad, but this choice gives us reason to doubt the scientist's hypothesis.

Choice D is the answer.

Here is my ananlysis of the argument:
Conclusion : "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."
THe author mentions that the increase in the amount of ferrous material in the atmosphere has increased the population of the algae in antartica. The only way to weaken this argument would be to show the decreament in the amount of algae in any way or to show that the decreament in the amount of algae is actually because of some other reason.
The reason why the author mentions the increase in the increase in the amount of algae is because of the decreament in the amount of CO2 in the atmosphere. So, the unhidden premise is that the number of algae during the last ice age is that
1. The decreament in the amount of CO2 cannot be done by the existing number of algae before or during the ice age, it had to increase and as mentioned in the argument due to the increase in population of algae the amount of CO2 decreased.
2. There is no other reason for the decreament of CO2 in the atmosphere of the antartic in the last ice age.

The only way to weaken the argument would be to attack the above 2 assumptions or something on the line of that.

Option (D) says that "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.", which esssentially means that the death rate of the algae practically remained the same and did not change throughtout the given period of time.

My question : IF my above explaination is correct, then on what basis are we claiming option (D) to be a weakener.

Kindly please help me clarify my understanding.
Sajjad1994 @KarsihmaB GMATNinja nightblade354

Samples of ice-age air are unusually high in ferrous material and unusually low in CO2, and one scientist believes that these two facts are related. It’s his theory that the ferrous material spurred an increase in the algae population, particularly diatoms; that increase in turn reduced levels of CO2, which algae consume. The problem is the absence of hard evidence of more algae; all we know is that if the population of algae increased, less CO2 would be expected. Evidence showing that there was no increase in the populations of algae in general (or diatoms in particular) would undermine the hypothesis, and choice (D) is it: Had the diatom population boomed, surely more of their shells would be around.

While I understood the intended meaning of option D and why it is correct, I interpreted it slightly differently. Can an expert please point out why my interpretation is wrong?

My Interpretation:
Count of shells didn't increase => count of Diatoms that died didn't increase (as they didn't leave shells) => More and more diatoms are present on the surface (as they seem to be living longer) => supporting the conclusion that diatoms increased during the ice age.

The main flaw in your reasoning is that you got the idea that "more and more diatoms are present on the surface" from nowhere.

Notice that you both decided that diatoms were living longer and that there were more of them without any evidence. All we know from (D) is that the rate of accumulation of diatom shells did not increase. There's no clear reason to believe that we can make the leap from that information to the ideas that there were more diatoms and that they lived longer.

Also, by the way, even if the diatoms did live longer, if there were more of them, then at a certain point, when many had lived for their longer lifespans, the rate of accumulation of shells would have increased. So, the idea that their living longer would have resulted in a long-term decrease in the rate of shell accumulation is also flawed.

I introspected as per what you have mentioned and what I have been thinking. What you said certainly makes sense. I couldn't thank you more MartyTargetTestPrep! Appreciate your efforts in clarifying our doubts.

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