第1个回答 2011-04-12
我就我想的起来的说几个:疑问句Must I ……?回答时,NO,you need not.
should have done sth.意思说(本应该做某事而没做)
should not have done sth.(本不应该做某事却做了)
need have done sth.(过去本来有必要去做某事但没有做)
need not have done sth .(过去本来没有必要做某事但却做了)
情态动词按照其可能性大小强度排是:must >can >may>might >ought to