shall和will;should和wouldshall have beenwill have beenshould have been would hane been它们分别要在什么样的情况下用哪个啊？
问题描述：
shall和will;should和would
shall have been
will have been
should have been
would hane been
它们分别要在什么样的情况下用哪个啊？
答
shall have done将来完成进行时,表示在将来某一时间以前已经完成或一直持续的动作.经常与before+将来时间或by+将来时间连用,也可与before或by the time引导的现在时的从句连用.will have done表示从将来的某一时间开...