YOU MUST have been driving at seventy miles an hour.这里去掉AT可以吗at的作用是什么

选择：You have been doing washing all the morning.You must be tired,( )you?A.mustn`t B.are C.aren`t D.must Dear! You must have been very happy now!是什么意思? It must have been so though for you,huh? must have been done must have done must have/ must have been的区别 Look at what you have done to my new book.You_____more careful with it.A.must have been B.might have been C.should have been D.ought to be You ______ when you heard the news.A、 must have been very excited B、 must be very excited C、 can be very excited D、will have been very excited 反义疑问句You must have been there before,______?A.have you B.did you C.haven't you D.didn't you请说明理由,还有一道You must have been in Beijing last month,_______ A.aren't you B.did you C.weren't you D.didn't you You should not have swum in that river.You ____ have been eaten by fish.A.must B.may C.will D.might When did you first visit China?I think it _____in 1996,when my parents were teaching in YunnanUniversity.A.must be B.should have been C.may be D.must have been其余选项为什么不对,尤其是A? You ( )be tired .you have only been working for an hour.A.must B.wont C.cant D.may not .You must do your homework now; you ______ computer games all the evening.A.have been playing B.play C.are playing D.played I phoned you at 9:00 this morning but got no answer.l am sorry .l _____ the bell.l____in the garden .A haven't heard,must have been.B didn't have heard,must beC didn't hear,must have been D didn't hear,must be 选哪个?为什么? The light in his office is out.He_________ left for home.A.must have B.must have been C.should have D.should have been he-----blind not to see that car cominga can hve been b will have been c may have been d must have been You ____ her in her office last Friday; she's been out of town for two weeks.A.needn't have been B.must have been C.might have been D.can't have been怎么看这里用不用虚拟呢? must not have been;could not have it-------- the manager the spoke to you just now/求解a can be b is C must have been D will be