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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27 Aug 2006, 17:17
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Scientists analyzing air bubbles that had been trapped in Antarctic ice during the Earthâ€™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 scientistâ€™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.

OA Later
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27 Aug 2006, 17:21
Going with C....
the passage says scients think ferrous material causes the growth of algae...but the answer choice c implies there are other materials found in the atmospheric dust...so other material other than ferrous can be the cause of algae growth..
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27 Aug 2006, 17:38
D..

The scientists hypothesize that there was a large number of diatoms but the ocean sediments do not reflect that..
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27 Aug 2006, 17:40
For me A

In C:
The dust found in the air bubbles trapped in Antarctica ice contained other minerals in addition to the ferrous material...but they dont say the magnitude of this material....what happen if it is 0.006%?
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27 Aug 2006, 22:08
Only (D) stays within scope and counters the scientists hypothesis. Why is there no evidence of the supposedly increased diatoms on the antarctic ocean floor?
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27 Aug 2006, 22:55
Cant really get what (D) means wud go for (C)
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28 Aug 2006, 03:30
GMATT73 wrote:
Only (D) stays within scope and counters the scientists hypothesis. Why is there no evidence of the supposedly increased diatoms on the antarctic ocean floor?

D for same reasons...
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28 Aug 2006, 03:45
D seems to be the only one within the scope of the argument.
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28 Aug 2006, 04:04
Going with (E). Whats the OA.
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28 Aug 2006, 04:33
C

(A) Diatoms are a microscopic form of algae that has remained largely unchanged since the last ice age.
out. bring nothing

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

(C) The dust found in the air bubbles trapped in Antarctica ice contained other minerals in addition to the ferrous material.
out- we don't know if the amount of the other minerals is larger than the "large amount" of ferrous materials. There could be only fews atoms, what could hardly weaken the arg.

(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.
ok - no increase rate of death-> could lead to no increase of rate of birth-> population=birth - death = constant->weakens.

(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.
doesn' weaken
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28 Aug 2006, 10:53
Should be between A and D.

Other options are out of scope.

A talks about last ice age ... not earth's last ice age.

D survives.
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28 Aug 2006, 11:04
OA is D..
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28 Aug 2006, 12:32
GMATT73 wrote:
Only (D) stays within scope and counters the scientists hypothesis. Why is there no evidence of the supposedly increased diatoms on the antarctic ocean floor?

Late, but agree with D.
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28 Aug 2006, 12:32
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