should , ought to , might 有什么区别、怎么用

should , ought to , might 有什么区别、怎么用
should , ought to , might , would , can , need , must , cought 之间有什么区别、怎么用?

解答情态动词表示猜测的试题时,一要清楚被猜测的时间,二要清楚有无客观事实根据.若有客观事实根据,则无论是肯定还是否定的猜测,猜测语气最强且符合时间要求的为最佳答案;情态动词表示猜测时语气从强到弱的顺序是:must,will,would,ought to,should,can,may,could,might.若无客观事实根据,纯凭主观臆断,则猜测语气最弱且符合时间要求的为最佳答案.如:
1.I thought you __________ like something to read,so I have brought you some books.(MET 1986)
A.may B.might
C.could D.must
由题意可知被猜测的时间是(过去)将来,没有客观事实根据,猜测语气要求最弱,所以正确选项是B.
2.Peter __________ come with us tonight,but he isn't sure yet.(MET 1993)
A.must B.may
C.can D.will
由题意可知被猜测的时间是将来,没有客观事实根据,猜测语气要求最弱,所以正确选项是B.
3.It __________ last night,for the ground was wet this morning.
A.must have rained
B.may have rained
C.must rain
D.might rain
由题意可知被猜测的时间是过去,有客观事实根据the ground was wet,猜测语气要求最强,所以正确选项是A.
4.Mary __________ be in Paris,for I saw her in the town only a few minutes ago.(MET 1994)
A.mustn't B.can't
C.shouldn't D.may not
由题意可知被猜测的时间是现在,有客观事实根据I saw her in the town a few minutes ago,猜测语气要求最强,所以正确选项是B(can't是m ust的否定式).
5?—There were already five people in the car but they managed to take me as well.
—It __________ a comfortable journey.(NMET 1995)
A.can't be
B.shouldn't be
C.mustn't have been
D.couldn't have been
由题意可知被猜测的时间是过去,有客观事实根据there were already five people...take me as well,猜测语气要求最强,所以正确选项是D.
6.—When can I come for the photos I need them tomorrow afternoon.
—They __________ be ready by 12:00.(NMET 1998)
A.can B.should
C.might D.need
由题意可知被猜测的时间是将来,有客观事实根据need them tomorrow afternoon,猜测语气要求最强,所以正确选项是B.
7.—Are you coming to Jeff's Party
—I'm not sure.I __________ go to the concert instead.(NMET 2000)
A.must B.would
C.might D.should
由题意可知被猜测的时间是将来,没有客观事实根据,猜测语气要求最弱,所以正确选项是C.
情态动词的推测性用法
用适当的情态动词表示讲话者对客观事物的主观看法,这就是情态动词的推测性用法.常用来表示推测的情态动词有 might,may,must,can.might,may,must表示的可能性程度由弱变强,must表示"一定", can则一般用于疑问句或否定句中.例如:
1.They must be talking about us on the radio right now.
此刻,他们一定在电台里谈论我们的情况.
2.She may have missed her train.
她可能没有赶上火车.
3.I don't know why he is late,he might have had an accident.
我不知道他为何迟到,可能遇上了事故.
4.Where can John have put the matches He can't have thrown them away.
约翰会把火柴放在哪儿呢 他不可能把火柴扔掉的.
5.That can't be the postman,it's only seven o'clock.
才七点钟,不可能是邮递员.
表示推测的情态动词后的动词不定式可用完成式,进行式和一般式三种.用完成式表示对过去情况的推测.例如:
6.Her father thought that she must have met a fairy.
她父亲认为她一定碰上了仙女.
7.They must have studied English for years.
他们学习英语肯定有几年了.
8.You may have left your glasses at the office.
你可能把眼镜忘在办公室了.
用进行式则表示对正在发生的动作的推测.例如:
9.He might be reading a newspaper now.
他可能正在看报纸.
10.He can't be working at this hour.
这个时候他肯定不会在工作.
推测性情态动词后用不定式的一般式有两种情况:如果不定式是状态动词,则表示对现在状态的推测.如果不定式是动作动词,则表示对将来动作的推测.例如:
11.Mary must have some problem ,she keeps crying.
玛丽不停地哭,一定有了麻烦.
12.I saw that the camel must be blind in the right eye.
我知道这只骆驼右眼肯定瞎了.
13.Our team must win the game.
=I'm sure that our team will win the game.
我们队肯定能赢这场比赛.
14.It might rain this evening.
=It's possi- ble that it will rain this evening.
今天傍晚天可能要下雨.
上述表明,推测性情态动词是以现在(讲话时)为基础,对过去,现在,将来的动作或状态的推测.因此,在构成陈述部分含有推测性情态动词的反意疑问句时,要注意反意疑问句中动词的不同形式.例如:
15.The boy must have thought John was mad,didn't he
那孩子肯定以为约翰疯了,是吗
16.Our teacher must have looked through our papers,hasn't he
老师一定批完了我们的试卷,是吗
17.She must be playing basketball,isn't she
她一定在打篮球,是吗
选择下列各句的正确答案.
1.Hurry up,our teacher _____ for us at the school gate.
A.must be waiting
B.must wait
C.might waiting
D.can be waiting
2.She doesn't answer the doorbell,she _____ be asleep.
A.might to
B.might
C.must have
D.should
3."What has happened to George ""I don't know,he _____ lost."
A.can have got
B.may have got
C.might get
D.could get
4.Mr Li _____ be in Beijing because I saw him in town only a few minutes ago.
A.needn't
B.can't
C.shouldn't
D.mustn't
5.We can't blame John for the mistake.He wasn't here when we decided what to do.So _____ he about the plan.
A.wasn't
B.was known
C.can't be known
D.couldn't have known
6.My ballpen is nowhere to be found,I _____ while I was playing football.
A.must drop it
B.should have dropped it
C.must have dropped it
D.had dropped
7.It _____ be Li Ming who took my dictionary away.It be Zhang Hua who did it.
A.can't;must
B.mustn't;must
C.needn't;can
D.may not;can
8.The streets are all wet;It _____ rained heavily last night.
A.should
B.should have
C.must
D.must have
9.Tom must have learned Chinese for several years, _____ he
A.mustn't
B.hasn't
C.didn't
D.don't
10.Mr Wang must be at home now, _____ he
A.mustn't
B.doesn't
C.isn't
D.wasn't
11.She must have left for Shanghai, _____ she
A.mustn't
B.hasn't
C.didn't
D.doesn't
Key:1.A2.B3.B4.B5.D6.C7.A 8.D 9.B 10.C 11.C
1) must/may/might + have done 表对过去动作、事实、状态推测
FOR EXAMPLE：
He must have arrived already. 他一定已经到了.
They may have seen him. 他们可能见到过他.
They might not have considered me as their friend. 或许他们没把我当成他们的朋友.
You might have let me known before! 你要是早点让我知道就好了.
It was really very dangerous. You might have injured him. 真是很悬.你有可能把他打伤了.
If I had been less cautious I might have seen more wise. 如果我不那么谨慎,或许反倒聪明点.
2. could/can + have done 表埋怨,能做的没做
could/can not + have done 表不能做的做了
FOR EXAMPLE,
You can have given me the book earlier. 你本来可以早点把书给我的.
You can not have forgotten me. 你不可能已忘记我了.
Indications are that the accident could have been prevented. 迹象表明,本来这次事故是可以避免的.
3.should/ought to + have done 表埋怨,该做的未做
should/ought not to + have done 表不该做的做了
FOR EXAMPLE,
He shouldn't have come to school at 9:00 am. 他不该早上9：00来上学.
He ought to have done the work himself. 这个工作他是应该自己做的.
They oughtn't to have let you out of hospital so soon. 他们不应当让你这么早出院.
肯定的+have done表示本应该做而实际上没做,否定的+have done表示本不应该做而实际上做了