can have done could have done should have done should to do shouldn't have done shouldn't to do
问题描述：
can have done could have done should have done should to do shouldn't have done shouldn't to do
还有
needn't have done
needn't do
mustn't have done
may not have done
might not have done
答
would/could /should/needn't+have done 表示本来……实际却没有
本来想要/能够/应该/不必做某事 而实际上却相反
must/may/might/can't+have done表示对过去发生的情况进行推测
过去一定是/可能是/也许是/一定不是
should to do/ shouldn't to do不存在
这些词都是情态动词 后面要么加动词原形 要么加have done那oughtn't to have done和oughtn't to do呢？oughtn't to have done属于第一类 ought to是情态动词词组 意义与should相同 这是否定形式 表示本来不应该做 实际上却做了oughtn't to do=shouldn't do 不应该做某事 情态动词的基本用法