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Nature constantly adjusts the atmospheric carbon level. An increase in the level causes the atmosphere to hold more heat, which causes more water to evaporate from the oceans, which causes increased rain. Rain washes some carbon from the air into the oceans, where it eventually becomes part of the seabed. A decrease in atmosphere carbon causes decreased evaporation from the oceans, which cause less rain, and thus less carbon is washed into the oceans. Yet some environmentalists worry that burning fossil fuels may raise atmospheric carbon to a dangerous level. It is true that a sustained increase would threaten human life. But the environmentalists should relax---nature will continually adjust the carbon level.

133. Which one of the following, if true, would most weaken the argument in the passage?

(A) Plant life cannot survive without atmospheric carbon.

(B) It is not clear that breathing excess carbon in the atmosphere will have a negative effect on human life.

(C) Carbon is part of the chemical “blanket” that keeps the Earth warm enough to sustain human life.

(D) Breathing by animals releases almost 30 times as much carbon as does the burning of fossil fuels.

(E) The natural adjustment process, which occurs over millions of years, allow wide fluctuations in the carbon level in the short term.

答案是e

請高手幫我想想  我困惑的地方

1. 題目的大概意思到底是說啥???

2. 題目所問的weaken the argument 是指 the environmentalists should relax---nature will continually adjust the carbon level.嗎?!

3. D選項那裡不妥?!

题目得出的argument is" the environmentalists should relax because the nature will continually adjust the carbon level to a safe level",

D只是说明动物呼吸比fossil fuels更容易使carbon level升高， 跟argument无关。

自然界可以持续不断的调节大气中碳的含量。含量上升会导致大气层变暖，使得更多的水从海洋中蒸发，从而雨水增多。雨水可以洗去空气中的部分碳到海里，最终那些碳变成了海底的一部分。碳在大气层中的含量下降会导致海水蒸发量下降，雨水减少，因此较少的碳会洗进海里。然而一些环境学家担心燃烧石油(?)可能会使得大气层中的碳达到一个危险的含量水平。如果这是真的，持续的碳含量增加将会威胁到人类生命。但是环境学家不需要这么担心——大自然会不断的调节碳的含量水平。

E中说明大自然调节作用是长期的，所以允许短期内碳含量水平巨幅波动。这就可能威胁到人类生命，所以环境学家担心的是有道理的，原文的结论被削弱了。

D中只是和动物的呼吸相比较，也不能得出燃烧石油不会使碳达到一个危险水平。也许本来就离危险水平很近的，加上燃烧石油的就达到了呢？虽然只是1/30，但是总量还是巨大的对吧？

真是謝謝你們的解釋

我完全理解了!!

真的很感謝!!