请教狒狒的两道题

Emily

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 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A
为什么？ A不是Strengthen吗

39. Quasars---celestial objects so far away that their light takes at least 500 million years to reach Earth---have been seen since 1963. For anything that far away to appear from Earth the way quasars do, it would have to burn steadily at a rate that produces more light than 90 billion suns would produce. But nothing that burns at a rate that produces that much light could exist for more than about 100 million years.
If the statements above are true, which one of the following must also be true on the basis of them?
(A) Instruments in use before 1963 were not sensitive enough to permit quasars to be seen.
(B) Light from quasars first began reaching Earth in 1963.
(C) Anything that from Earth appears as bright as a quasar does must produce more light than would be produced by 90 billion suns.
(D) Nothing that is as far from Earth as quasars are can continue to exist for more than about 100 million years.
(E) No quasar that has ever been seen from Earth exists any longer

这里的D& E 不是等同的答案吗？
为什么是E?[em01][em01][em01][em01][em01][em01]

yuw99gmat

38 题
only 表明排除他因（ozone )，（直接反对了结论）,是一个绝对结论。有一点点绕。

stoneren

有理

卧室春竹

我觉得 38 关键说的是 Thus, the primary cause of the declining amphibian population is the depletion of the ozone layer. 就是ozone得消失..

UV-B这个东西是不是唯一损害GENES无所谓吧！

关键看结论... 加强总的加强结论吧？！

stoneren

39.D和E是不一样的。
D：没有距离这么远的东东可以维持100M的生命。
E：我们所能看到的quasar已经exists了。
而文中只强调了quasar的生命是100M，却没有任何暗示表示是否有其他XX的生命如何如何。
事实上，文中表达的意思是quasar的光线要500M年才能达到地球，而其寿命才100M，所以可以推出，当quasar的光线达到地球的时候，这个quasar已经消失了至少400M了。

38.Sorry,我也很困惑，不过又发了新贴，希望有人回，你可以查阅。