would should migt could have done有什么不同

would 将
should 应该
might 也许
could 可能
have done 已经做了
have done 可以加在前面四个单词后面,表示过去将来时
I would have done my homework if you didn't call me.
如果你没给我打电话,我已经做完作业了.
You should have done your homework before coming here.
你来之前应该做完作业的.
He might have seen that before.
他之前也许看过了.
They could have called us.他们可能给我们打过电话了.