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.
(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.
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.
Answer is C , in my opinion.
We need to undermine the scientists hypothesis that "ferrous material had promoted increase in algae" ...
OPtion C says , "there were couple of other stuffs found in the air bubbles trapped in the ice" , gives us a reason to believe that something else might have promoted an increase in algae - and hence doubt scientists hypothesis that ferrous is responsible for an increase.
Whereas, Option D , undermines the premise , but not the scientists hypothesis/conclusion. The premise says that there was an increase in algae then. D only lets us know that there might not be an increase in the algae back then . But we are not supposed to undermine the premise and rather are supposed to take it to be true. In this view, D does nothing to undermine the conclusion that "ferrous led to the increase in algae".
HTH
Jyothi