Critical Reasoning

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 net 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.

Apologies if this has been posted before, I am still not clear on why B is not 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 depend
s?

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 net 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.

Conclusion: The tranquilizer is CAUSING the lower fertility rates.

An ASSUMPTION is WHAT MUST BE TRUE for the conclusion to be valid.
Apply the NEGATION test.
When the correct answer choice is negated, the conclusion will be invalidated.

C, negated:
ANY STRESS that female rhinoceroses may suffer as a result of being immobilized and handled HAS A HUGE EFFECT on their fertility.
The negation of C indicates that STRESS HAS A HUGE EFFECT on fertility, invalidating the conclusion that the TRANQUILIZER is responsible for the lower fertility rates.
Since the negation of C invalidates the conclusion, C is the correct assumption: WHAT MUST BE TRUE for the conclusion to be valid.

The correct answer is C.

Tmoni26 wrote: I am still not clear on why B is not the correct answer

B, negated:
The fertility rate of uncollared female rhinoceroses in the park has NOT been increasing in the past few decades.
The negation of B seems to STRENGTHEN the conclusion that some substance in the tranquilizer inhibits fertility.
Since the negation of B does not invalidate the conclusion, eliminate B.

HI Mitch,

Thanks alot for the response