一道语法题请教

司马忆云 · 发表于 2012-5-5 15:35:18

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
E.   of humans who were known to make

我选了C
date不能用when指代么？应该是what is the date? 还是when is the date?
还用我觉得官方选项中的C用了完成时似乎没什么道理

司马忆云 · 发表于 2012-5-5 18:05:34

司马忆云 · 发表于 2012-5-6 08:07:48

upup

司马忆云 · 发表于 2012-5-7 13:19:02

UPUP 啊啊啊

sphinxzhang · 发表于 2012-5-7 14:54:03

http://forum.chasedream.com/GMAT_SC/thread-389550-1-1.html

scarlett006 · 发表于 2012-5-7 14:56:47

有个固定搭配叫be to known to do/be to know to have done，后面的和前面的时间一致就是to do，有先后关系就是have done

司马忆云 · 发表于 2012-5-7 22:03:16

懂了，谢谢啦

本贴相关题目 GMATPrep-2008E1-SC-256 | TN-12-SC-1 (XWHK)

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