Diatoms

gmatmachoman 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?

Premise : Ice age atmosphere contained large numbers of ferrous material and small amount of carbon di oxide
Premise : Algae absorb carbon dioxide from the atmosphere

Conclusion : Ferrous material had promoted increase in algae population of antartica

A) Diatoms are a microscopic form of algae that has remained largely unchanged since the last ice age.
INCORRECT : Irrelevant. Diatoms is only used as an example in the stimulus. Furthermore this answer choice does nothing to weaken the conclusion.

(B) Computer models suggest that a large increase in ferrous material today could greatly promote the growth of oceanic algae.
INCORRECT : Strengthens the argument by stating that ferrous material could indeed 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.
CORRECT : This undermines the argument by stating that there is possibility of some other cause (other minerals) for the stated effect (increase in algae population).

(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.
INCORRECT : Irrelevant/ Out of Scope

(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.
INCORRECT : Irrelevant. Issue is not about harm caused to algae by ferrous material.