CR-08prep-74求解

Evangeline13

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.  utting 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.  robably, 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

請問為什麼答案是C啊?他不是在討論tranquilizer會不會抑制生育，那跟how often有甚麼關係呢?  麻煩各位了!!

单调唱

[quote]
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.  utting 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.  robably, 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

premise1:as often happens, a collar slips off, it is put back on.
premise2utting a collar on a rhinoceros involves immobilizing the animal by shooting it with a tranquilizer dart
premise3: Female rhinoceroses that have been frequently recollared have significantly lower fertility rates than uncollared females.
Conclusion:some substance in the tranquilizer inhibits fertility.

Pay attention to premise1 and premise2, the author assume that collars often slip, so rhinoceros are often been shoot by tranquilizer darts, it means that the main difference between Female rhinoceroses and uncollared females is the amount of tranquilizer.

But we cannot deny that maybe park rangers use tranquilizer darts to immobilize rhinoceroses mostly for other reasons such as experiment. If so, something other than tranquilizer may have more impact on rhinoceros.

it is true that collars often slip and as a consequence, rhinoceros are often been shoot by tranquilizer darts. But it cannot be true that rangers use tranquilizer darts to immobilize rhinoceroses for reasons only to or mostly to attach radio collars. So the author cannot conclude that the main difference between Female rhinoceroses and uncollared females is the amount of tranquilizer.

naoyixue

http://forum.chasedream.com/archiver/GMAT_CR/thread-413832-1.html
倒数第4个选项，太好了

Evangeline13

thank you so much

牛掰

单调唱 发表于 2012-4-29 09:28
[quote]74.    (29534-!-item-!-188;#058&004138)In a certain wildlife park, park rangers are ...

又看见你的回答了，纠结了我半天，明白了，谢谢！