情态动词
【情态动词】
又叫情态助动词。它们具有以下 特点:
⑴ 它们必须与其他动词连用,即: 情态动词+动词原形
表示说话人对所述动作的看法,如需要、可能、意愿或怀疑等。
⑵ 绝大多数情态动词 没有人称和数的变化 ,即第三人称单数不加 -s (以 be 和 have 开头的情态动词短语除外 )。 ⑶ 在意义上,情态动词具有 “多义性 ”。 例:can 既可表示能力,又可表示可能、允许等意义。
【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 ’kteep 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 ’bte 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 ’表t 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 ,, ?
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— 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’/tdon’thave 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. Shemust 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 ’htave 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 togo 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 youneed 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 ’tetll 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 butyhe coat. 你没有必要买那件外衣。(你还没买)
You needn ’ t have bougthhte 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’/tdon’thave 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 neetdo work today. (= We needn ’wtork today.) Does he need to go right now? (= Need he go right now?)
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6. had better 的基本用法:
had better 常略作 ’ d bette。r 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 bettegr et some sleep. 你最好睡一会儿。 You ’ d better nodt o 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’twe 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 he此re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 ’不t,.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’ to bme. 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 numb王er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。
一、 典型例题【中考链接】
( )1.— Who is the man over there? Is it Mr. Li? — No, it ______ be him. Mr. Li is much taller. A. mustn ’t B. may no C. can ’ t D. needn ’t
(
)2.— Must I go with them tomorrow ?
— No,you ______.
A. mustn't B. shouldn't C. needn't D. can't
( )3.— ______ I take some photos in the hall?
— No, you ______.
A. Can, needn ’tB. Must, mustn ’ tC. Could, won ’ t D. May, mustn ’t
( )4.— Dad, must I finish my homework today? — No, you ________. You may do it tomorrow. A. needn ’ t B. mustn ’ t C. don ’ t D. won ’t
( )5.— The lake is said to be dry. Is that true? — It _______.Look, some kids are swimming in it. A. must be true
B. can ’ t be true
C. may not be true
(
)6.— What is your mother going to do this Saturday? — I ’ m not surSe.he _____ go to see my grandmother. A. can B. must C. may
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( )7.—Susan has bought a large house with a swimming pool. —It ______ be very expensive. I never even dream about it. A. must B. might C. can ’t
D. shouldn ’t
( )8.—Listen! Is Professor Johnson giving a report in the hall?
—No, it be him. He has gone to Japan. A. needn ’t B. may not C. mustn ’t D. can ’t
(
)9.—Let ’s go to the West Hill Park by taxi.
—Oh, it is not far away from here. We _______take a taxi.
A. couldn ’t B. mustn ’t C. needn ’t D. can ’t
( )10.—Can you play the piano?
—Yes, I _______. I often practice it on weekends. A. needn ’t B. need C. can ’t
D. can
三、课后练习
一、用 can, may, must, need, have to, had better 的适当形式填空: 1. You ________________ return the library book on time.
2. I ______________ (not) find the way to the hospital. _______________ you show me the way? 3. —________________ I finish the work right now?
— No, you ________________ (not). You ____________ do it later. 4. He said he ________________ (not) come tonight.
5. Her mother was ill. She ________________ stay at home and look after her.
6. It ’s time for class. You ________________ stop playing football or you __________be late for class. 7. We ________________ start right now, or they would get there first.
8. The cloud is lifting, so it ________________ (not) be a rainy day tomorrow. 二、选择填空
( )1.—Do we have to finish our homework this afternoon?
—Yes, you ________.
A. must B. can C. may D. need ( )2. —Must I be in hospital for a week , Doctor?
—No, you
. You can go back home tomorrow.
A. mustn ’t B. needn ’t C. must ( )3. The desk is not dirty. You _______clean it. A. mustn ’t
B. shouldn ’t
C. needn’t
C. can ’t
( )4. —May I watch TV for a while ?
—No, you _______. You have to finish your homework first.
A. shouldn
’t B. needn ’t
C. mustn ’t
D. won ’t
( )5.—Is Jessica giving us a speech this evening?
—No, it ________be her. She________ to Japan.
A. mustn ’; thas gone B. mustn ’t ;has been C. can ’t ;has gone D. can ’t ;has been
( )6. It ’s the library! So you________ know shouting is not allowed here. A. can B. must C. need D. may ( )7. Boys and girls, don’t forget your report . It ______ today.
A. can ’t finish
B. can ’t be finished C. should finish
D. should be finished
( )8.—Mr Smith must have been to your home this morning. —No, he ______ ,because he didn ’t know my address. A. couldn ’t B. can ’t C. mustn ’t D. may not ( )9. —Must I mop up the window now?
—No, you________.
A. needn ’t B. can ’t C. shouldn ’t D. mustn ’t ( )10. —Is Lucy knocking at the door? —No. It ________ be Lucy. She is in Japan now. A. needn ’t B. must C. can ’t ( )11. —Another cup of coffee?
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— No, thanks. I _____ be off. Mary is waiting for me. A. can B. may C. must D. might ( )12. — I ’m a little tired. Let ’s go to the zoo by taxi.
— We take a taxi. It ’ s not far from here.
A. can ’ t B. mustn ’ t C. couldn ’ t D. needn ’t ( )13. If the traffic light is red, you ________ cross the road. It ’s very dangerous. A. don ’ t B. mustn ’ t C. needn ’ t D. wouldn ’t ( )14. — Must I finish watering the flowers now? (
— No, you________. A. must B. won ’ t C. needn ’ t )15. — I can ’t give up smoking, doctor. D. can ’t
— For your health, I A. may B. can ’ m afraid you ________. C. have to
D. must
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