请教一道OG题

adameye

OG10中38. 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 non-amphibian 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：D

 

D中，如果over the past century改成是over the last 50 years,能成为排除他因的strengthen么？

mbz

以下是引用adameye在2006-7-7 9:45:00的发言：

答案：D

 

D中，如果over the past century改成是over the last 50 years,能成为排除他因的strengthen么？

that depends on the density of the Amphibian populations

adameye

以下是引用mbz在2006-7-7 10:14:00的发言：

that depends on the density of the Amphibian populations

已知是populations are declining in numbers，答案是栖息地没有变小，应该是排除了栖息地减少造成population减少的因素，不应该存在population密度的问题啊.

gnefiahihs

如果over the past century改成是over the last 50 years,是不是与原文结论无关了