PT19.S2.Q04 - scientists analyzing air bubbles

dennisgerrard

I can't see why (E) is wrong. Could anyone explain why (D) is right?? Appreciate in advance
https://7sage.com/lsat_explanations/lsat-19-section-2-question-04/

Waiting For Grey Day

I think in order to explain Why E is wrong and Why D is right, we should address the components of the argument first, just to make sure we understand the structure of it. This always helps me to really understand the subtleties of relationships under the clutter.

Context: Ice-Age air has unusally large amounts of ferrous material and small amount of CO2.

Premise (fact given): Algae absorbs CO2 from atmosphere

Scientist's Hypothesis (The argument we are dealing with):
Ferrous material promotes greater increase in Antartic algae population (i.e. diatoms)

So here, I think the scientist is trying to explain why ice-age air had so much ferrous but such small amounts of CO2. He think there is an indirect relationship between ferrous material and CO2, where algae is the link. (Ferrous generates algae population, where more of algae absorbs more of CO2).

Why is E wrong?

Ice-age is the temporal scope the argument is working with. Comparing how current algaes react "not appearing to be harmed" to ferrous materials has no effect on the hypothesis, and so it does not weaken the argument. If we were to attack the argument, we would need to undermine the link, which is the algae population.

Why is D correct?

D provides additional evidence: sediments show no increase in the accumulation of diatoms shells. In other words, the rate of death of diatoms did NOT increase during the last ice age (time is within scope). If the rate of diatom shell accumulation did not increase, then ferrous material did not increase the population of diatoms. This directly undermines the argument.

I think D is hard to understand because it requires us to infer that the rate of increase in algae population during the ice age also means that there would be increase in death of those algaes during the ice age found later in sediments.

I hope this helped!

dennisgerrard

@"Color Me Grey" Thanks for bringing up the time scope concept.