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Scientists have dated sharp-edged flakes of stone found in the fine-grained sediments of a dry riverbed in the Afar region of Ethiopia to between 2.52 and 2.60 million years ago, pushing back by more than 150,000 years the earliest date when it is known that humans made stone tools. A. when it is known that humans made B. at which it is known that humans had made C. at which humans are known to have made D. that humans are known to be making (C) E. of humans who were known to make
A选项里的it为什么不能做形式主语呢？真正的主语是that humans made... 一直搞不懂it啥时候能当形式主语啥时候是具体指代啊？？ 祝好心的NN们帮忙！
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发表于 2017-9-8 16:38:40
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发表于 2017-9-8 17:04:27
