All can be done has been done.A. whatB. thatC. whichD. the one

问题补充：

All can be done has been done.

A. what

B. that

C. which

D. the one

答案：

A. what

(答案→)B. that

C. which

D. the one

解析：这里要填一个关系代词来引起定语从句…can be done,由于先行词是all,所以选 that.