这题老题 老错

斯巴达

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

windypig123

时态问题吧。
A 。it...made 不搭
B 。it....had made不搭，而且原句没有过去完成时的标志词
C. 没有用完成时
D.我觉得that修饰DATE怪怪的，而且这里是强调的过去时间 ，而不是说人们现在正在making
E。 正确

不知道我说错了么。欢迎拍砖啊。。
LZ也不公布答案