新PREP 74

dengyichao

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
我还是不太理解C，如果不经常，park rangers不经常因为其他理由给犀牛打镇定剂，就说明是镇定剂抑制了犀牛的生育能力，这我理解，可是如果park rangers经常因为其他理由给犀牛打镇定剂，就说明不是镇定剂抑制了犀牛的生育能力吗？

719870465

原文，被反复安装雷达的犀牛生育能力低于没有安装雷达的。反复安装雷达是需要打镇定剂的。所以作者说是镇定剂中的某种物质让犀牛是去了生育力。
反驳。如果不被反复安装雷达的犀牛也总是打镇定剂，换句话说，不管带不带雷达，犀牛打差不多次数的镇定剂。那么既然两者镇定剂量一样，就反驳了原文。比如我举个例子，两只犀牛一个反复带，一个不带，打同样次数的镇定剂，要是还出现带的生育低，就知道镇定剂不是问题，很有可能是雷达的辐射使得犀牛不生育。

demonada

我终于想明白了，关键就是那个对比~如果说管理员很少使用镇定剂不是为了给犀牛重带项圈，那么老是重带项圈的犀牛就比不带的被注射的多很多，说明可能是镇定剂让母犀牛们生育能力下降：但是呢，如果管理员老用镇定剂打犀牛不是为了带项圈，那么很可能不带项圈的母犀牛用的镇定剂和戴的母犀牛一样，甚至还多，那怎么能说是镇定剂的问题呢？。。。。。。。好难想到呀~这题得好好啄米琢磨的

liuli_beryl

突然间明白了。因为是用Female rhinoceroses that have been frequently recollared 和uncollared females对比。如果说后者也经常因为其他原因被镇静剂麻醉的话。那么怎么解释两者之间存在的significantly lower fertility rates呢？所以说如果镇静剂只因为装那个radio collars时候使用其它情况不用，那就strengthen;反之，就说明这个繁殖力的差异并非镇静剂导致的，而是其它某些原因，weaken

liuli_beryl

顶起来！！！

liuli_beryl

我选了B，为什么不行呢？请牛牛帮忙解释一下

prayer

可能跟文章中的那个frequently有关系吧，答案也就是C好些

prayer

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
我还是不太理解C，如果不经常，park rangers不经常因为其他理由给犀牛打镇定剂，就说明是镇定剂抑制了犀牛的生育能力，这我理解，可是如果park rangers经常因为其他理由给犀牛打镇定剂，就说明不是镇定剂抑制了犀牛的生育能力吗？

-- by 会员 dengyichao (2010/3/9 15:00:36)

这道题我对选项C不是特别认同，主要是那个often。
后半部分应该是对的，文章说重新装回去那个东东就要打tranquilizers，装了雷达的母犀牛比没装的雷达的生育力差，所以tranquilizers里的物质抑制了犀牛的生育力。
其实这里有个假设的，就是没装雷达的母系牛不需要打tranquilizers，文章只说了雷达掉了会打tranquilizers，没说其他原因。
这里如果需要评价的话，就需要看看是否存在其他原因也打tranquilizers。
对于C的how often，我不理解，其他的都好说。

dengyichao

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