
1，would/wouldn't have done
Would/wouldn’t have done表虚拟常用两种句型(if/but),
含义：某人会/不会做某事 某事会/不会发生
I would have helped you, but I didn’t know you needed help.如果我知道你需要帮助，我会去帮你的。（当初没帮）
I would have passed the exam if I had worked hard如果我努力学习，我是会通过考试的。（实际没通过）
The result wouldn’t have been so bad if you had taken my advice.如果你听了我的建议，结果不会这么糟。（实际结果很糟）
2，could have done
Could have done表虚拟常用两种句型(if/but)
含义：1）某人有能力做某事 某事有机会发生
2）轻微的指责
I could have passed the exam if I had worked hard.
I could have passed the exam but I didn’t work hard.如果我努力学习了，我可能就能通过考试了。（没通过）
You are so late. You could have called.
你来的太晚了。你本可以给我打个电话（我可以先去别的地方待会儿）
3，might/might not have done
Might/might not have done表虚拟常用if
含义：某人可能会做某事；某事可能会发生
某人可能不会做某事； 某事可能不会发生
If you had given her more chances, she might have achieved greater progress.如果你当初给了她更多机会，她可能就会取得更大的成绩。（当初没给多机会）
If you hadn’t given her more chances, she might not have achieved so great progress.如果你当初没给她更多机会, 她可能不会取得这么大成绩。（当初给了很多机会）
4，
should/should not have done
Should/shouldn’t have done表虚拟常单独使用/用but
含义：应该做但没做；不该做却做了:
I really shouldn’t have ignored your advice.
I should have taken your advice, but I didn’t.我当初真应该听你的（当初没听，后悔）
You should have taken my advice.你当初应该听我的（当初没听，指责）
