bobohard,otherwiseheinthisexamA.can'thaveworked;wouldn'thavefailedB.can'twork;wouldn'thavefailedC.mustn'thaveworked;wouldn'tfailD.musthaveworked;wouldfailAmanansweredthephone.Isupposeitwasherhusband.Itherhusband.

Question

bobo __hard,otherwise he___ in this exam
A.can't have worked ;wouldn't have failed
B.can't work;wouldn't have failed
C.mustn't have worked;wouldn't fail
D.must have worked;would fail
A man answered the phone.I suppose it was her husband.
It__ her husband. He has been dead for ages.
A.mustn't be B.mustn't have been
C.couldn't be D.couldn't have been.
he___ be in hospital.I met him in the library only a moment ago
A.can't B.mustn't C.may not D.shouldn't

Answer 1

1.A
原因：bobo（）用功,否则他（）考试.意思先猜一下,他要再用功些,否则他就过不了考试.或者是：他可能没有好好用功,否则他不会过不了考试的.
B错在,后面用了虚拟,前面没有用语法上不对.
C的意思是,他不可以再用功,否则他不会通不过考试的,wouldn't fail双重否定,表示通过考试,意思和逻辑上是错的,所以不对.
D- must have done,是肯定在过去做了什么事的意思,他肯定用功了,否则他会“would fail”没过考试,逻辑上错误,也不对.
A：can't have done,不可能过去做了什么,前半句的意思是他不可能之前用功了,otherwise he wouldn't have failed,否则他不会失败.意思、语法和逻辑都正确.
2.C
原因：一个男人接了电话,我猜可能是她老公.它（）她老公,死了几年了.（）处肯定应该是（不可能）,整个句子是过去时,表示过去不可能用could not be
3.A
原因：can't 是不可能的意思（现在时）,mustn't是不允许的意思,本句意思是：他（不可能）在医院里,我几分钟前刚在图书馆里遇见他,所以用can't,而不是mustn't.may not-可能不是,但因为刚碰到,所以很肯定不可能用can't,shouldn't是不应该的意思,只有A正确.