请教天山7-41

3bao

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

 

请大家帮忙讲解一下A和C吧 呵呵 如果各个选项都能讲一下就更好了 (*^__^*)  

SHJDHKBB9

B had made时态不对;

D to be making被动表达含义不合逻辑;

E 改变原义且含义表达不合理;

至于A和C,我认为A更好,C at which 表示一个时间点,而后面有接 have made(有从过去开始后一直进行的含义),同时本句的意思是"向前追溯更早的时间点",因此我认为在此句中C不如A一般过去时made表达更清晰准确.

个人意见,请问答案是?

k2o33

另外，如果选c，就成了人类以做石器而出名了吧

3bao

答案是C 呵呵~~

SHJDHKBB9

原来如此.

AlienX

C是在強調made這個動作比known早

mjiehu

A的问题出在it is。到底是现在知道，还是以前就知道