I think I have tried my best.All that can be done ___.

问题描述:

I think I have tried my best.All that can be done ___.
A.has done B.has been done C.had done D.had been done
为什么选B不选D

我认为我已经尽力了,所有能做的都做了.All that( can be done)has……和I think I have……里的have同时态.表示现在已经,从现在来看.过去完成时,是过去的过去,要有一个过去的时间点才行.这题是讲现在.