GRE 里一道逻辑题,请赐教!Editorial:Critics of nuclear power complain about the allegedly serious harm that might result from continued operation of existing nuclear power plants. But such concerns do not justify closing these plants;after all

GRE 里一道逻辑题,请赐教!Editorial:Critics of nuclear power complain about the allegedly serious harm that might result from continued operation of existing nuclear power plants. But such concerns do not justify closing these plants;after all
GRE 里一道逻辑题,请赐教!
Editorial:
Critics of nuclear power complain about the allegedly serious harm that might result from continued operation of existing nuclear power plants. But such concerns do not justify closing these plants;after all, their operation has caused no more harm than that caused by pollution generated by coal-and oil-burning power plants, the most important other sources of energy.
Which of the following is an assumption on which the argument depends?
(A) Existing nuclear power plants should be closed only if it can be conclusively demonstrated that their continued operation is likely to cause harm more serious than the harm their operation has already caused.
(B) Closing existing nuclear power plants would require greatly increased reliance on coal-and oil-burning power plants.
(C) The harm that has resulted from operation of existing coal-and oil-burning power plants has been significant.
(D) The harm that a nuclear power plant is likely to cause as it continues to operate can be reliably predicted from the past history of nuclear power plants.
(E) The only harm that has resulted from operation of existing coal-and oil-burning power plants has resulted from the pollution generated by these plants.

答案是D,我真心没明白...

GRE 里一道逻辑题,请赐教!Editorial:Critics of nuclear power complain about the allegedly serious harm that might result from continued operation of existing nuclear power plants. But such concerns do not justify closing these plants;after all
原题：
结论：核电站的批评者抱怨现有的核电站连续工作的后果可能很严重.但是其担心不足以关闭核电站.
原因：因为毕竟核电站运行的害处并未曾比煤矿、石油电站这些更重要的能源工业所产生的污染更严重.
（注意原文中的现在完成时,核电站运行至今尚未造成比传统能源工业制造的污染更大的危害.如果要得出不足以关闭核电站的结论,假设应该是从以前的运行情况可以推断出今后的运行情况,所以核电站连续运转可能会出大危害的担心是没有必要的）
A.只有演示出核电站连续运行会导致比目前运行更严重的后果时,才应关闭现有核电站.
（这个不是假设,是个结论）
B.关闭现有核电站会需要更加依赖煤矿和石油煅烧的电站.（这个是推论,不是假设）
C.现有的传统电站运行导致的危害已经很大了.（这个文中没有说,只是把核电与传统电站相比,说不比其严重.而且从原因到结论并不是靠这个假设的.）
D.正确的假设
E.现有传统能源工厂运行中的唯一危害来自其产生的污染.（这个太武断了,看见the only harm基本就可以用排除法排除了.同时这也与原因结果无关.）

their operation has caused no more harm，现在完成时，表示至今为止核能所造成的污染并没有化石燃料造成的多。他是根据过去的情况推测现在的，如果过去的情况不能RELIABLY 推测出现在的话。。这个结论是不成立的吧。。has been 只能说明至今为止，并没有说以后发展核能会带来的污染。（只是随便看看。。不要批我。。）...

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their operation has caused no more harm，现在完成时，表示至今为止核能所造成的污染并没有化石燃料造成的多。他是根据过去的情况推测现在的，如果过去的情况不能RELIABLY 推测出现在的话。。这个结论是不成立的吧。。has been 只能说明至今为止，并没有说以后发展核能会带来的污染。（只是随便看看。。不要批我。。）

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