74. (29534-!-item-!-188;#058&004138)
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.
In evaluating the argument, it would be most useful to determine which of the following?
A. Whether there are more collared female rhinoceroses than uncollared female rhinoceroses in the park
B. How the tranquilizer that is used for immobilizing rhinoceroses differs, if at all, from tranquilizers used in working with other large mammals
C. How often park rangers need to use tranquilizer darts to immobilize rhinoceroses for reasons other than attaching radio collars
D. Whether male rhinoceroses in the wildlife park lose their collars any more often than the park’s female rhinoceroses do
E. Whether radio collars are the only practical means that park rangers have for tracking the movements of rhinoceroses in the park
答案为C
我对于这个答案不是很理解，当时我选D的，考虑的是是否是female自身的问题导致了fertility不高的原因。
题目的结论是tranquilizer中的某些成分inhibits fertility，而C选项的意思却是告诉我们除了collare以外，还有其他的原因让rhinoceroses去接受tranquilizer。那么判断的结论应该是由于collared导致了low fertility rates.
难道是我的思路错了吗？
请一定指教！
结论是：麻醉弹里的有些物质导致了低生育率。
得出这个结论的前提是：那些经常性被重新上领圈的母犀牛有较低的生育率。
那么如C所说，如果这些麻醉弹用在别的用途，而不是上领圈对母犀牛的话，也许就无法说明这些物质导致了低生育率。
D。公的犀牛丢失领圈的情况对这个解释这个问题来说是无关的。（这个要素不是我们要讨论的）
C. How often park rangers need to use tranquilizer darts to immobilize rhinoceroses for reasons other than attaching radio collars
如果回答是park rangers often need to use tranquilizer darts to immobilize rhinoceroses for reasons other than attaching radio collars,说明uncollared females也会经常被投射麻醉弹，但是uncollared females的fertility rates并不像frequently recollared rhinoceroses那样低，可以推出tranquilizer darts不会导致low fertility rates。
如果回答是park rangers not often need to use tranquilizer darts to immobilize rhinoceroses for reasons other than attaching radio collars,同理可得low fertility rates可能是由tranquilizer darts导致。
D.无关选项
希望对你理解由帮助噢~
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