Source: Official Guide for GMAT Review 2016 Critical Reasoning; #11

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# Which of the following, if true, most helps to

Which of the following, if true, most helps to explain the decline in the population of the fish species?

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John Robertson

Q: Why is there a decline in a fish species, despite a decrease in the population of its main predator, the alligator?

Important supporting info: there has not been an increase in the annual number of fish caught by humans to eat. Something else is happening

A: WRONG. Fishers may be working the waters more because less alligators, but the prompt says the number caught hasn't gone up. So human catching fish is not the cause for the fish declines.

B: WRONG. same reason as A.

C: Correct. The prompt pretty clearly leads you to read that humans aren't the cause of the fish declines, so something is at work. Less alligators (main predator), humans aren't catching more (another main predator), what is decreasing the fish? Leads you to think pollution, another predator of the fish that is also benefiting from less alligators, etc. This answer answers that theory well of "who/what other than humans and gators are declining the fishes"

D: WRONG. We know alligators are declining, irrelevant background information.

E: WRONG. same as D essentially

Jan 4, 2017 • Comment