上海牛津英语情态动词的基本用法讲解及练习.doc

情态动词的基本用法
1. can的基本用法：
⑴ 表示体力或智力上的能力，即“能够，会”，可与be able to转换。
例：He can speak English. = He is able to speak English. 
—Can you play basketball? 
— No, I can’t. 
如果表示将来具备的能力，要用will be able to。
例：If I have a good sleep, I will be able to do the problem. 
⑵ 表示许可，主要用于口语，书面语一般用may。
例：—Can we go home now, please? 
— No, you can’t. 
You can only smoke in this room. 
You can’t keep the library books for more than a month. 
⑶ 表示“可能”，与may同义，但一般用在疑问句中。
例：What can he possibly want?
在否定句中，否定形式can’t表示推测“不大可能”。
例：Anybody can make mistakes. 
The news can’t be true. 
与第一、二人称连用时，还可以就可能的解决问题的方式或可能的行为提出建议。在这里，也可用could使语气婉转。
例：Can / Could we meet again next week?  下周我们可以再见面吗？
—What shall we do?  我们怎么办呢？
— We can / could try asking Lucy for help. ——我们可以请露茜帮忙试试看。
You can / could help me with the cooking.  你可以帮我做饭。
2. may的基本用法:
⑴ 表示“许可”，用can比较口语化。
例：You may / can come if you wish.  如果你想来，你就来。
You may not pick flowers in this park.  本公园内不许摘花。
（may not表示按规定不许可，如果用mustn’t则表示说话人不许可。）
—May I smoke here?  我可以在这里抽烟吗？
—No, you mustn’t. 不行。（mustn’t表示明确的禁止。）
⑵ 肯定句中表示推测，“可能”。
例：It may rain tomorrow.  明天可能会下雨。
The news may not be true.  这个消息可能不会是真的。
注意：如果在疑问句中表示“可能”，通常用can。
例：Can it be true?  那会是真的吗？
Who can he be?  他究竟是谁呢？
⑶ 【注意】：—May I/we……？
—Yes, you may./—No, you mustn’t. 

3. must的基本用法:
⑴ 表示必须，强调说话人的主观意志。
例：I must go now, or I’ll be late. 
You must be here by ten o’clock. 
【注意】：表示“必须“时，must的否定式为needn’t ，或don’t have to ,而不是mustn’t。
也就是：—Must I/we do it now？
—Yes, you must .
—No, you needn’t /don’t have to . 
例：—Must I go with them? 
—No, you . 
⑵ 表示推测，一般只用于肯定陈述句,表示非常肯定。
例：She didn’t look at me. She must be angry.  她不朝我看，一定是生气了。
He is good at English. He must know the word.  他英语好，准知道这个词。
You must be Mr. Jones.  想必您就是琼斯先生吧。
4. have to的基本用法：
have to可视为情态动词，但它与其他情态动词在用法上稍有不同。其他情态动词没有人称和数的变化，而have to却有人称和数的变化，要视主语的不同而变化。
例：I / You / We / They have to….
He / She / It has to….
You don’t have to….
Does she have to…?
have to =have got to，意思是“必须，不得不”。
和must不同之处：must强调主观需要
have to强调客观需要。
例：Sorry, I have to leave now.  对不起，现在我得走了。
I’ve got to go to a meeting.  我得去参加一个会议。
Will he have to work deep into the night?  他将不得不工作到深夜吗？
5. need的基本用法：
need的基本词义是“需要”，它既可作情态动词，又可作实义动词。
⑴ need用作情态动词时，只用于否定句和疑问句。它只有一种形式，后接动词原形。
例：I don’t believe you need worry.  我相信你没有必要焦急。
—Need we go so soon? 我们需要这么早就去吗？
— Yes, we must. / No, we needn’t.  是的，必须。／不，不必。
So I needn’t tell him, need I?  所以我不需要告诉他，对吧？
请比较以下两句话的不同意思：
You needn’t buy the coat.  你没有必要买那件外衣。（你还没买）
You needn’t have bought the coat.  你没有必要买这件外衣的。（而你却买了）
【注意】：—Need I/we……？
—Yes，you must ./—No, you needn’t / don’t have to .

⑵ need用作实义动词时，有时态、人称和数的变化。
如果人作主语，一般后接带to的动词不定式。即need to do sth；
如果物作主语，一般后用need to be done 或need doing sth。
例如：I need to look up this word in the dictionary. 
My watch needs mending/to be mended.  我的手表需要修理了。
We don’t need to work today.  (= We needn’t work today.) 
Does he need to go right now?  (= Need he go right now?) 
6. had better的基本用法：
had better常略作’d better。现代语法认为它是一个助动词，因为它后接不带to的动词不定式。
had better do sth意思是“最好做某事；还是做某事比较好”。
例：You’d better get some sleep.  你最好睡一会儿。
You’d better not do that again.  你最好别再做那件事。
What had we better do now?  我们现在怎么做才好呢？
Hadn’t we better tell her the truth?  我们是否最好不告诉她真相?
【注意】：You’d better….表示劝告或委婉的命令，对长辈不宜使用。
7. could, should, would, might表示推测：
①. must多用于肯定句中表示把握性极大的推测,意思为“一定、肯定”。
如: You have worked hard all day. You must be tired. 你已辛苦工作一整天了,一定累了。
The book must be his. His name is on the cover. 这本书一定是他的,封面上写着他的名字。
【注意】 must不表推测时,在肯定句中意思为“必须(强调内在的职责)”,在否定句中意思为“不许、禁止”,以它开头的疑问句否定回答常用needn’t或don’t (doesn’t) have to。
如:We must obey the traffic rules. 我们必须遵守交通规则。
Cars mustn’t be parked here. 此处严禁停车。
—Must we hand in the papers this week? 我们必须本星期交论文吗?
—No, you needn’t. 不,你们不必(本星期交)。
②. can / could多用于否定句、疑问句或感叹句中表示推测、怀疑,两者在时间上没有差别。用can时不相信的程度更强一些, can’t常常译为“不可能”。
如:The man under the tree can’t be Tom. He’s gone to England. 这个人不可能是Tom,他已经去英国了。
Can it be true that he was fooled by a five-year-old boy? 他被一个五岁的孩子愚弄了,这能是真的吗?
Could this be an excuse? 这会不会是个借口?
How can you be so careless! 你怎么这样粗心!
③.may / might多用来表示把握性不大的推测,意思为“也许、可能”, might比may的把握性更小一些。
may not在否定句中常常译为“可能不”。(注意区分“不可能”与“可能不”在把握性大小上的差异。)
如:Mr. Wang may know Professor Li’s telephone number.王先生也许知道李教授的电话号码。
This might be the key Tom has been looking for.这可能就是汤姆一直在找的钥匙。
She may not be there today. 今天她可能不在那儿。

情 态 动 词

（ ） 1. Mr. Wang ______ be in Nanjing now, he went to Beijing only this morning.
A. mustn’t B. may not C. can’t D. needn’t
( ) 2. –Must I stay at home, Mum? --No, you ______.
A. needn’t B. mustn’t C. don’t D. may not
( ) 3. –Can you go swimming with us this afternoon?
--Sorry, I can’t. I _____ take care of my little sister at home because my mother is ill.
A. can B. may C. would D. have to
( ) 4. –May I go to the cinema, Mum? --Certainly. But you ______ be back by 11 o’clock.
A. can B. may C. must D. need
( ) 5. To make our city more beautiful, rubbish ______ into the river.
A. needn’t be thrown B. mustn’t be thrown
C. can’t throw D. may not throw
( ) 6. –May I go out to play basketball, Dad?
--No, you ______. You must finish your homework first.
A. mustn’t B. may not C. couldn’t D. needn’t
( ) 7. –Where is Jack, please ? --He _____ be in the reading room.
A. can B. need C. would D. must
( ) 9. The boy said he had to speak English in class, but he ______ speak it after class.
A. could B. didn’t have to C. might D. shouldn’t
( ) 10. John ______ go there with us tonight, but he isn’t very sure about it.
A. must B. can C. will D. may
( ) 11. Even the top students in our class can’t work out this problem. So it ______ be very difficult.
A. can B. may C. must D. need
( ) 12. Put on more clothes. You ______ be feeling cold with only a shirt on.
A. can B. could C. would D. must
( ) 13. It’s still early. You ______.
A.     mustn’t hurry B. wouldn’t hurry
C. may not hurry D. don’t have to hurry
( ) 14. –Could I borrow your dictionary? -- Yes, of course you _______.
A. might B. will C. can D. should
A. needn’t B. can’t C. should D. may
( ) 15. ______ I know your name?
A. May B. Will C. Shall D. Must
( ) 16. You ______ be more careful next time.
A. have to B. may C. must D. might
( ) 17. This pen looks like mine, yet it isn’t. whose ______ it be?
A. must B. may C. would D. can
( ) 18. What kinds of homes will we live in the future? Nobody ______ be sure, but scientists are working out new ideas now.
A. will B. may C. can D. must
( ) 19. I ______ like to know where you were born.
A. shall B. should C. do D. may
( ) 20. ______ you be happy!
A. Might B. Must C. Wish D. May
( ) 21. A teacher ______ do every exercise, but a student must.
A. may not B. needn’t C. can’t D. mustn’t
( ) 22. The matter ______ be changed into a gas, but it _______ be heated to its boiling point.
A. may; needn’t B. may; can
C. mustn’t; needn’t D. can; must
( ) 23. Teachers and students ______ look coldly at you for a day or two, but there are friendly feelings in their hearts.
A. must B. can C. may D. should
( ) 24. Cars and buses ______ stop when the traffic lights turn red.
A. can B. need C. may D. must
( ) 25. –Do you think his story ______ true? --I don’ think so. But it sounds good.
A. must be B. may be C. can be D. has to be
( ) 26. –How long ______ the book be kept?
--For two weeks, but you ______ return it on time.
A. can; may B. may; need C. can; must D. must; need
( ) 27. –Shall I tell John about the bad news?
--No, you ______. I think that will make him sad.
A. needn’t B. wouldn’t C. shouldn’t D. mustn’t
( ) 28. –Could I call you by your first name? --Yes, you ______.
A. will B. could C. may D. might
( )29. –Let’s go to the cinema, shall we? -- _______.
A. No, I can’t B. Yes, I will
C. Yes, thank you D. No, we’d better not
( ) 30. --______ the man there be our new teacher?
--He ______ be, but I’m not sure.
A. May; mustn’t B. Can; may C. Must; can’t D. Can; can’t
( ) 31. –Someone is knocking at the door. Who ______ it be?
--It ______ be Tom. He is still in the school.
A. can; can’t B. can; mustn’t C. might; could D. might; may

答案：
1—5 CADCB 6—10 ADbD 11—15 cDDCa 16—20 cdcbd
21—25 BdCdc 26—30 CdcdD 31 A

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