[讨论] 求助：一道非常难的逻辑题

喵喵猫

小女子目前在北美LSAT 备考中。。。遇到一道个人认为百思不得其解的逻辑题，恳请各位牛人赐教！！！谢谢~

这是一道Strengthen的题目。

1.       Amphibian populations are declining in numbers worldwide. Not coincidentally, the earth’s ozone layer has been continuously depleted throughout the last 50 years. Atmospheric ozone blocks UV-B, a type of ultraviolet radiation that is continuously produced by the sun, and which can damage genes. Because amphibians lack hair, hide, or feathers to shield them, they are particularly vulnerable to UV-B radiation . In addition, their gelatinous eggs lack the protection of leathery or hard shells. Thus, the primary cause of the declining amphibian population is the depletion of the ozone layer.

Each of the following, if true, would strengthen the argument EXCEPT:

A.      Of the various types of radiation blocked by atmospheric ozone, UV-B is the only type that can damage genes.

B.      Amphibian populations are declining far more rapidly than are the populations of nonamphibian species whose tissues and eggs have more natural protection from UV-B.

C.      Atmospheric  ozone has been significantly depleted above all the areas of the world in which amphibian populations are declining.

D.      The natural habitat of amphibians has not become smaller over the past century.

E.       Amphibian populations have declined continuously for the last 50 years.

答案是A。。我选的D， 谁能告诉我为什么是A 吗？？？

谢谢~

dphxmg

If besides UV-B, there were other types of radiation which can damage genes and which are also blocked by ozone, the conclusion would probably be strengthened. 

D strengthens the argument by excluding another possible reason for the decline in amphibian population: the shrinking natural habitat.

喵喵猫

Thanks for your post. but it's still pretty confusing to me.

As in answer choice A, now I can see it makes sense is that , the conclusion of the agmt that " the primary cause of the declining amphibian population is the depletion of the ozone layer." has nothing to do the UV-B. and the agmt didn't talk abt anything that the ozone layer has been depleted is caused by UV-B.

But for D, why it strengthens the agmt?

thanks.

喵喵猫

OH!! I C why D is wrong!!thanks~

greenteatalk

反过来想，如果D不成立，也就是The natural habitat of amphibians has  become smaller over the past century，那么这个原因可能也可以解释"Amphibian populations are declining".

那么D如果成立，就不存在“habitat变小”这个原因可以解释amphibian数量减少，也就是从另一个方面加强了题目中的论述，即the primary cause of the declining amphibian population is the depletion of the ozone layer.

shishen_lsy

但我选A的理由是，感觉A选项和strengthen the argument 无关，而并非因为否A有strengthen 的作用

jocelyne123

A doesn't strengthen or weaken. D basically gives an alternate cause to the population decline.

lemongrass07

 哈哈 你这题和我选的是一样一样的 bible上说 D选项是排除他因了

stoneseen

d excluded an alternative cause. Maybe you will say a excluded the possibility that other radiation, rather than uvb, caused the decrease in population, but pls be careful: the conclusion is "the primary cause of the declining amphibian population is the depletion of the ozone layer"

gerrardlfc08

D排除他因