GMAT Prep Verbal - CR

[SahithiT896]

While this question has been answered in the past, it had different answer choices. When I tried using the same logic when reviewing this question, I wasn't able to understand the correct answer.

In a certain wildlife park, park rangers are able to track the movements of many rhinoceroses because those animals wear radio collars. When, as often happens, a collar slips off, it is put back on. Putting a collar on a rhinoceros involves immobilizing the animal by shooting it with a tranquilizer dart. Female rhinoceroses that have been frequently recollared have significantly lower fertility rates than uncollared females. Probably, therefore, some substance in the tranquilizer inhibits fertility.

Which of the following is an assumption on which the argument depends?

A. The dose of tranquilizer delivered by a tranquilizer dart is large enough to give the rangers putting collars on rhinoceroses a generous margin of safety.

B. The fertility rate of uncollared female rhinoceroses in the park has been increasing in the past few decades.

C. Any stress that female rhinoceroses may suffer as a result of being immobilized and handled has little or no negative effect on their fertility.

D. The male rhinoceroses in the wildlife park do not lose their collars as often as the park’s female rhinoceroses do.

E. The tranquilizer used in immobilizing rhinoceroses is the same as the tranquilizer used in working with other large mammals.

Correct Answer: C
My Answer: B

Thanks!!

[Sage Pearce-Higgins]

This is a classic Assumption question, and it's definitely worth being clear about what an assumption is before proceeding. I suggest reading this post: https://www.manhattanprep.com/gmat/forums/post130517.html

For this argument, the conclusion is "Probably, therefore, some substance in the tranquilizer inhibits fertility" (the word 'therefore' helps us here) and the rest of the passage is either background information or premises (support for this conclusion). We're looking for a gap in the argument that represents a missing piece of information that the argument needs in order to work. That's an assumption.

I actually found this one pretty clear because I took time to think: "well, these females get lower fertility after being tranquilized, but is it actually the chemical that is causing the lower fertility, or could there be some other reason? Maybe something else happens during the process of reattaching the collar that causes their fertility to decrease?". After thinking that, then answer C stands out as a likely answer, but I can confirm it using the negation test (check out the CR Strategy Guide for more on this - feel free to post again if you have trouble applying it here to answers C and B).

[SahithiT896]

Thank you! I did take a look at those articles and tried using the negation test, but I thought since the answer choice mentioned males, and the argument only talks about females, that couldn't be the right answer. I see I incorrectly removed that now.

However, I still am unable to see how the assumption supports the argument. Could you try to explain it in a different way maybe?

Thank you, I appreciate it!

[Sage Pearce-Higgins]

You're right that answer choice C doesn't seem to strengthen the argument in very visible way. However, I would contend it strengthens the argument by removing one of alternative explanations. This argument follows quite a common pattern: it makes a claim about causation based on evidence about events occurring in a regular pattern (correlation). This is often called the correlation-causation fallacy. It's actually really hard to prove causation, and I'd recommend training yourself to be suspicious when you see conclusions that involve causation and to take time to imagine alternative causes. Let me give you a simpler example:

Every Sunday morning Joe wakes up with a terrible headache (premise). Every Saturday evening Joe goes out drinking in a bar (premise). Therefore, I think his Sunday morning headaches are caused by his drinking on Saturday evenings (conclusion).

Take a minute to criticize this argument before reading on. Hopefully you thought of alternative explanations for his headaches - things like loud music, bad sleep, medication, staying up late, migraines, etc. For the argument to work, we need to assume that these are not the real explanation for his headaches - that the only thing that causes his headaches is his drinking the night before. So, if I said 'Joe is not on any medication that causes headaches' then that strengthens the argument by removing an alternative explanation. Note that it doesn't make the argument perfect - there are still other gaps to be filled.