求助reasoning！！！

lihaolan

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.
D是什么意思。。。答案是D

玛莎丁丁

The stimulus basicially says that:
Premise1: Large amounts of FM and Small amounts of CD in air bubbles during last ice age
Premise2: Algae absorb CD
Conclusion: hypothesis that FM promoted algae's population, such as diatoms
And it asks what choice Weakens the conclusion

D tells us that from what is left in the sediment, no evidence shows that diatoms' population increased. This strikes the conclusion directly.
I think it is clear that A,B and E strengthen or at least does no harm to our conclusion. C could be temping at first sight. C introduces "other minerals" into consideration which suggests that there could be "other minerals" that promoted the algae instead of the FM. (Also...it might not. we are not given enough info) However, compared to D, it doesn't attack the conclusion as directly. That's why D is a better choice.

Hope it helps. Let me know if I didn't make it clear enough.