could have been done ,could have

could have been done ,could have 有must/could/can/may/maight have been done吗 could/should/must/.加have done和have been done区别 will be done和will have done是什么情况could have been呢 could never have done could not have done must have been done must have done 虚拟语气 if You could have done other career What would it have been 为什么不是 if ..Had done 句 Could have done would have done should have done 英汉互译 If we had been given more time,we could have done it better could never have done 造句 how could you have done could have been could have been have been done 和 to be done have been done 语法呢 can be done was done could be done must have been done will be done have been done用这些,每个造一个句子.上面的打错了can be donewas donecould be donemust have been donewill be donehave been done would have done,might have done,could have done,should have done分别表示什么意思?