For years, the leading theory for what caused the Younger Dryas (a dramatic reversal, about 12,900 years ago, in a global warmin

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问题     For years, the leading theory for what caused the Younger Dryas (a dramatic reversal, about 12,900 years ago, in a global warming trend) was a release of water from Glacial Lake Agassiz. The theory posited that this meltwater flooded into the North Atlantic, lowering the salinity and intensity of surface waters enough to prevent them from sinking. Ocean currents were changed in such a way that northward transport of heat in the ocean diminished, and the North Atlantic regions plunged back into near-glacial conditions. However, evidence has emerged that the Younger Dryas began long before freshwater flooded the North Atlantic. Additionally, the temperature changes included by a shutdown in the North Atlantic heat conveyor system are too small to explain the Younger Dryas.
The passage is primarily concerned with

选项 A、presenting evidence that undermines an explanation
B、explaining the nature of a climatological phenomenon
C、questioning the timing of a particular event
D、discussing a new explanation for a phenomenon
E、suggesting revisions to a popular theory

答案A

解析 本文为驳论文,因此主旨应该是“反驳了……”,答案可以锁定在选项A和选项C。A项an explanation对应老观点对新仙女木期发生原因的解释,evidence对应however后两句,起到反驳作用,因此选项A正确。B项a climatological phenomenon可以认为对应新仙女木期,但是本文没有讨论新仙女木期的本质是什么一C项a particular event指的是新仙女木期,其发生时间是客观事实,在文中没被反驳,因此选项C不正确,D项本文是驳论文,只有批判,没有新观点,所以选项D错在new,E项revisions意为“修正”,不仅仅有批判,还要提出新观点,但是本文没有新观点。
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本试题收录于: GRE VERBAL题库GRE分类
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