Some soil scientists have asserted that decaying matter on the forest floor is a far greater source of the acidity in mountain l

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问题 Some soil scientists have asserted that decaying matter on the forest floor is a far greater source of the acidity in mountain lakes than is the acid rain that falls on these lakes. Therefore, they contend, reducing acid rain will not significantly reduce the acidity levels of mountain lakes. Which of the following statements, if true, most seriously weakens the argument above?

选项 A、It is natural for mountain lakes to have acidity levels higher than those of other lakes.
B、The harmful effects of increased acidity levels in lakes have been greatly underestimated.
C、Acid rain is found in urban and heavily industrialized regions of the country.
D、There is much disagreement among soil scientists about the causes of acid rain.
E、While plant life remains, acid rain significantly increases the amount of decaying organic matter in natural environments.

答案E

解析 若我们用A’表示森林里的腐烂物质,用A代表酸雨,用B表示山中湖泊酸性增加,那么段落推理可表示为“A’,not A→B”。当段落推理说不是某一原因导致某一结果时,反对大多为“就是这个原因导致了某一结果”,因此应用A中的关键词来定位选项。“A’,not A→B”推理模式的反对思路有二:①就是A导致了B;②A导致了A’。(E)通过指出A导致了A’,起到了反对作用,所以(E)为正确答案;(A)、(B)、(C)、(D)均为无关选项。
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