PREP软件里的一道题，想不通。。。

guanwzy

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, 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 usd 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 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.
答案是C，何解。。。

guanwzy

啊，明白了，多谢！

Luxe

原题的逻辑是，频繁的 recollared的母H比uncollared的母H怀孕率低，所以可能是麻醉剂里有避孕物质。
D选项是 除recollared外，对H使用麻醉剂的频率。
如果是除了recollared外，使用麻醉剂的对象就不局限于collared和uncollared。对象是整体的母H。
如果除了recollared外，使用频率很高的话，说明整体的母H都有大量接触麻醉剂的可能性。
从而推断出 recollared的母H比uncollared的母H怀孕率低，可能与麻醉剂无关。

guanwzy

那个。。。我不太会搜索。。。

wangsiwei

楼主可以搜一搜以前的帖子，讲的挺清楚的。

guanwzy

我还是无法理解，即使如楼上所说，tranquilizer also used for reasons other than attaching radio collars，我们也只能知道recollar和lower fertility rates可能无关，但不能推出tranquilizer和lower fertility rates无关啊。。。

buda

I think here we need to evaluate whether frequently recollared have significantly lower fertility rates than uncollared females has relationship with tranquilizer
If tranquilizer also used for reasons other than attaching radio collars, there is no direct relationship between tranquilizer and recollared lower fertility rates