should have done
本该做到但是没有做到
如:
you should have won the game,but you failed.
你本该赢了那场比赛,但是你输了.
shouldn't have done
本不该做的而做了
如:
you shouldn't have watered the flowers.
你本不该浇花的
could have done
本可以做而没有做
如:
you could have worked out the question,but you didn't
你本该解出拿到题的,但是你没有
couldn't have done
就不要我说了吧 类推~