【请教】GWD-T-4-Q1 TS-7-41

hduszj

T-4-Q1 TS-7-41     

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

答案：D

为何用完成时，不理解？

A为何不对？

请各位大侠指教！！！

edmundshi

答案应该是C～

date,age,time用定语从句修饰时用which而不用when

B中it指代不明

boo0330

it是虛主詞啊 代替後面的that 子句，我只能覺得B錯是 過去完成式不對，或是 it is ... that...太囉嗦...
說it 指代不明好像太牽強

lu80

答案应该是C～date,age,time用定语从句修饰时用which而不用whenB中it指代不明

-- by 会员 edmundshi (2009/7/10 12:42:00)

edmundshi版主

1、请问it it known that不是强调句型吗？GMAT是不是不喜欢这种句型吗？
如果it指代不明，那么it还指代什么？为什么会指代不明？

2、humane are known to have made中的have made 是过去完成使的转换形式吗？

谢谢！