[求助]一道GWD语法题

haoyushare · 发表于 2010-2-22 19:12:19

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 know 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

答案选A

BCE很快排除，就不用讨论了。

请教一下 D 错在哪里，另外 to be doing 的用法。

感谢！

haoyushare · 发表于 2010-2-23 12:34:24

那是答案错了，谢啦！

cannahere · 发表于 2010-2-23 10:00:12

C对的

表示那时候人类已经开始制造石器了

haoyushare · 发表于 2010-2-23 09:08:02

C时态不对吧？

liverpool123 · 发表于 2010-2-22 23:18:57

这个题目应该选择C

A读起来太绕口了，C明显很好

[求助]一道GWD语法题

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