another 2

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.

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.

新手上路

Rank: 1

精华: 0
积分: 41
经验: 41 点
威望: 0 点
金钱: 66 ￥
魅力: 41

8^#

zy发表于 2002-8-12 18:57 | 只看该作者

No.39 should be E.

According to the passage, it takes the QUASARS 1 million years to burn out and 5 millions for its light to arrive at the Earth. Of course, when we catch the first sight of its light, QUASARS already no longer exits - It was burn out 4 million years ago.

If the answer D was expressed in the following way it would surely be ok:

D. Nothing that is as far from Earth as quasars are "and burns at a rate that produces that much light" can continue to exist for more than about 100 million years.

Looking forward to your comment. Tks.

TOP