难题：一道未讨论过的Prep CR，望牛牛赐教，O(∩_∩)O谢谢

请教各路牛人：

        我在Prep的CR部分遇到这样一道题，编号为：Version of 53 questions-Q74，题目同GWD,但题型和答案全不同，答案选C,很是费解，望牛牛不吝赐教，O(∩_∩)O谢谢！！！

74. 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

原文其实在premise和conclusion之间有个 assumption，就是 tranquilizer里面有 那些特定的substance。 原文给蜗牛的低生育率提供了一种说明，就是受到 那些substance的影响。

C，其实是提供了一个对于他因是否存在的判断。如果C成立，即 蜗牛们常常被注射，那么 高注射率 本身有可能导致了 低生育率。这时就有两个原因，高注射率和特定substance同时存在，究竟那个导致 低生育率，就不好说了。也就是 C如果是真的，那么削弱结论。

C 如果不成立，那么高注射率这个外因就被排除，于是就成为了排除他因的加强。

所以 如果C成立，weaken原文结论，不成立strethen原文结论，就是很好的evaluate的选项。

其余的都是out of scope的选项。

谢谢楼上的详细分析过程O(∩_∩)O

我这样理解你的意思不知对否：

有可能不是:注射剂本身导致不育；而是：老打针，受惊了，导致不育。

有一点我很费解:

C. How often park rangers need to use tranquilizer darts to immobilize rhinoceroses for reasons other than attaching radio collars

这里的 other than attaching radio collars，也有点out of scope.

原因：本文discussed的是：因要recollar而注射=>导致低生育率，choice C说：other than attaching radion collars,也是out of scope.

鄙人认为：如果choice C改为--How often park rangers need to use tranquilizer darts to immobilize rhinoceroses to attach radio collars,才相关。

不知各位牛人意下如何，烦请大家集思广益,O(∩_∩)O谢谢！！！

嗯，楼主MM这么说也有道理。

For example，如果 C不成立，那么 蜗牛 还有可能因为要被 attach collar 而常常需要被注射，也是就高注射率的在C成立的情况下 还是无法排除。

倒是如果C成立，高注射率的 这个外因就被加强了。结论被weaken （蜗牛们平时 有事没事都要被打针....)

这么说来 C成立 可以 weaken结论,但是C不成立，原文结论不能被strengthen.

有可能我的考虑还有欠缺。。。。。

谢谢楼上的关注和详细解答 O(∩_∩)O

望各位牛人能顶囊相助，帮我解答这个疑惑，O(∩_∩)O谢谢！！！

本题我当时做的时候也选错了。

因为我目标不是满分，所以对于对于纠结的题直接PASS了

惭愧惭愧

13兄，没想到在这也能遇见你。谢谢你的整理的JJ。

这题我也做错了，感觉全都out of scope. C是五个选项中最接近答案的了。不管什么为了原因给犀牛扎针，都会对犀牛造成惊吓，从而导致不孕。C应该是“排除他因”加强。

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。