OG70. His studies of ice-polished rocks in his Alpine homeland, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets existed in what are now temperate areas. 我想问一下exist为什么用过去时，怎么不用过去完成时呢。因为exist是发生在led之前的啊。。。。
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发表于 2010-6-4 21:22:04
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