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CR 1000

Expert replies
by amitu » Tue Jun 29, 2010 5:59 am
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

between C and D which one to eliminate and why ?
OA D
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Source: — Critical Reasoning |

by albatross86 » Tue Jun 29, 2010 6:25 am
FACT 1: Ice-age atmosphere contained large amounts of ferrous material and small amounts of CO2.
FACT 2: Algae absorb CO2

Conclusion: Ferrous material promoted increase in population of algae.

WEAKENER:

A. Algae are the same as before - irrelevant.

B. More ferrous => More algae - Strengthener.

C. Dust contained OTHER minerals. So what? The conclusion is w.r.t. the ferrous material being unusually large, i.e. the comparison between today's amount of ferrous material with the ice-age one. The argument doesn't depend on any other minerals not being or being there.

D. During ice age, rate at which algae died remained the same. Assuming death rate is constant, we can say that if the population had increased, number of deaths should have increased. But it did not - this weakens the conclusion that the population increased greatly.

E. Ferrous material does not harm algae - Irrelevant.

Pick D.
~Abhay

Believe those who are seeking the truth. Doubt those who find it. -- Andre Gide
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