虚拟语气中，would have done，should have done，coul

虚拟语气中，would have done，should have done，coul

虚拟语气的句子按道理是应该配套用的：主句had done +从句would have done。

could have done也表示虚拟语气，它的含义是“本来能做但没有做”，如He could have passed the exam.(本来能考及格但是没有)。
might have done：①表示对过去某事的推测，认为某一件事情在过去可能发生了。如果使用might，语气就比较婉转或更加不肯定，如：Mary might have learned some Chinese before.
②可以表示过去本来可以做到而实际没有做到的事情，有“劝告”或“责备”的语气，如：You didn't do the work well that day. You might have done it better.
should have done只用于谈论过去情况，主要有两个用法：①用于推测过去已经发生的情况。如：He should have arrived by now. 此时他本该到了。②用于指本该发生而实际上未发生的情况。如：You should have told me so before. 你早就应该告诉我


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