Unit8 情態動詞和助動詞
一、考點聚焦
1、 情態動詞的基本用法
(1)can、be able to 和could
①can和be able to都表示能力，意思上沒多大區別。但can只有現在和過去時，而be able to則有更多的形式。但當成功地完成某一具體動作時，通常不用could而用was/were able to來表示。這時was/were able to 相當于managed to，表示經過一番努力，終于能夠完成某事。如：
Can you use chopsticks?
The wounded man still was able to get to the village and was saved in the
end.
②can和could
can和could都可以表示能力、技能、許可、建議或請求和可能性。但比較委婉客氣地提出問題或陳述看法，一般用could，回答時則用can。如：
Could you help me carry the bag?
Can I help you?
(2)may/might
①may/might表示可能，但may比might可能性大。如：-Why isn’t he in class?
He may be sick.(生病的可能性較大)
-
He might be sick.(生病的可能性較小)
②may/might表示“允許”，may用于現在時或將來時，might常用在間接引語中表過去時，但might也可用于現在時間，表示比較委婉的語氣，回答用may。如：
He says we may leave.
He said we might leave.
③may / might 表示建議或請求，但might比may 更客氣，意思更肯定而無過去時態的含義。
Yes, you can / may.
-May / Might I use your bike? -
No, you mustn’t
（3）must
①must表示必須，應該，沒有時態變化。如：
You must do everything as I do.
②must表示肯定的推測。如：
The light is still on, so he must be at home.
③mustn’t 表示禁止做某事。如：
You mustn’t smoke in the office.
（4）have to
have to 表示“必須、不得不”，是由于某種外界（客觀）原因而“必須”，“不得不”做某事，也可表示經常的或習慣性的事“必須”做。have to的否定形式表示不必。have to可用于多種時態中。如：
You will have to clean your own boots when you join the army.
I have to be at my office every evening.
（5）should / ought to
①should和ought to表示應當、應該，前者比后者語氣輕。如：
You should / ought to work hard.
②should / ought to work hard.
Since she is not here, whe should / ought to be in the classroom.
③should / ought to的否定形式表示禁止之意。如：
Children shouldn’t smoke.
④should可表示陳述意見，推出建議或請求；而ought to可以表示勸告之意。如：
You ought to respect your parents.
He suggested that they should leave at once.
（6）will / would
①will 用于各種人稱表示“意志”、“意愿”或“決心”等，否定式won’t + 動詞。如：
I will tell you all about it.
Tom won’t do such a thing.
②will用于疑問句中，常用在第二稱時表示說話人向對方提出“請求”或“詢問”如：
Will you please tell her the news when you see her?
③will 表示習慣性的動作，有“總是”、“慣于”的含義。如：
Fish will die out of water.
④would 表示客氣的請求、建議或意愿。如：
Would you please be quiet?
Would you like coffee?
⑤would 表示過去反復發生的動作。如：
When I passed my school I would see my teachers who taught me 5 years ago.
（7）need
need 作“必要”講，既可作情態動詞，也可作實義動詞。作實義動詞時后面的動詞不定式要帶to，其變化與一般動詞相同。如：
I need to think it over.
-Need you go now? -Yes, I must./No, I needn’t
（8）dare
dare表示“敢”的意思。作為情態動詞時，主要用在疑問句和否定句中。dare若作實義動詞，后面可帶to的不定式，此時to也可以省略。dare與need的用法相似。如：
How dare you say that?
She doesn’t date(to)ask her father.
（9）used to
used to表示過去常常發生的動作或存在的習慣，但現在已不復存在了。如：
He used to smoke.
（10）shall
①shall作為情態動詞用于第二、三人稱，表示說話人的意愿，有“命令”、“警告、威脅、強制”和“允許”等意思。如：
We shall do as our teacher says.
You shall have the book as soon as I finish it.
②在疑問句中，shall用于征求對方的意見或請求指示，常用于第一、第三人稱。如：
Where shall he wait for us?
Shall we go out for a walk?
2、情態動詞表示推測或判斷的用法
下表即是表示推測的情態動詞使用的場合：
情態動詞 對現在和未來的推測 對過去的推測 使 用 場 合
must must + 動詞原形 must have done 肯定句
may / might may / might + 動詞原形 May / might have done 肯定句、否定句
can /could can / could do Can / could have done 否定句、疑問名（could可用于肯定句）
should 用來表示一種估計的情況“按理會/估計會”should do/be should have done 肯定句、否定句、疑問句
例如：
It must have rained last night.
She may not be at home. = It is possible that she is not at home.
She can’t be at home. = It is impossible that she is at home.
They should be there right now.
3、情態動詞在虛擬語氣中的用法
情態動詞用于虛擬語氣中表示責備的感情色彩，用法如下：
（1）should have done表示“本來應該做某事而實際上未做”，而shouldn’t have done則表示“本不應該做某事而實際上做了”。如：
You should have told me about it earlier.
You shouldn’t have said such words to your parents.
（2）ought to have done也表示“本應該……”而ought not to have done則意為“本不應該……”。如：
You ought to have told me about it earlier.
You ought not to have said such words to your parents.
（3）needn’t have done表示“本無必要做某事而實際上做了”。如：
You needn’t have walked so quickly since time was enough.
（4）could have done表示“本來有可能……而事實上未做到”。如：
I could have come on time, but my car broke on the way.
二、精典名題導解
選擇填空
1. I was really anxious about you. You________home without a word.(NMET 2001)
A.mustn’t have B.shouldn’t have left
C.couldn’t have left D.needn’t have
解析：答案為B。本題考查的是情態動詞在虛擬語氣中的用法。題目給出的條件是“我確實非常擔心你”，因此后面可知應是責備you不應該沒說一句話就離開了。
2.-Are you coming to Jeff’s party?
-I’m not sure. I__________ go to the concert instead.(NMET 2000)
A.must B.would C.should D.might
解析：答案為D。本題考查情態動詞的基本用法。由題目中“I’m not sure”,表明我可能去Jeff’s party，也可能去音樂會，故用might。
3. -Will you stay for lunch?
-Sorry, ____________. My brother is coming to see me.(NMET 99)
A.I mustn’t B.I can’t C.I needn’t D.I won’t
解析：答案為B。本題考查表示請求的英語口語，用will來向第二人稱提問的疑問結構，是表示一種請求和意愿，是用疑問的形式來表達較為婉轉的祈使語氣，意思是“請你……，好嗎”，對于這種問句的肯定回答是：Suree! Gertainly! Yes, of course. I’d be glad to 等；否定回答通常是：I’m sorry, I can’t. No, I’m afraid I can’t. I’m sorry, but … I’d like to, but …等。注意情態動詞表客氣的用法及其在一般疑問句中的問與答。
三、專項訓練
1. -Jack certainly has a low opinion of Janny.
-It_______than hers of him.
A.can’t be any worse B.can be any worse
C.can be some worse D.can’t be more worse
2. She_______be at home because she phoned me from her office just now.
A.mustn’t B.needn’t C.can’t D.shouldn’t
3. The big fire last night_______the whole building.But the heavy rain helped.
A.might be burning down B.should have been burned down
C.could have burned down D.must have been burned down
4. I want to go to the dentist,but you_______with me.
A.need not to go B.don’t need go C.need not go D.need go not
5. -Must we take a bus?
-No,you_______,You can walk from here.
A.must not B.don’t have to C.don’t must D.don’t need
6. You_______return the book now.You can keep it till next week if you like.
A.can’t B.mustn’t C.may not D.needn’t
7. -Could I borrow your dictionary?
-Yes,of course you_______.
A.might B.will C.can D.should
8. -May I stay here for another day?
-No,you_______.
A.mustn’t B.might not C.needn’t D.won’t
9. -You ought to have helped her yesterday.
-Yes,I know I_______.
A.ought to B.ought to have
C.ought have done D.ought to have called
10. -_______he open the door?
-Yes,please.
A.Shall B.Will C.Can D.Would
11. Whatever difficulties we_______with,we’ll go on with the experiment.
A.meet B.met C.shall meet D.may meet
12. In the end they_______save the cat on the roof.
A.could B.were able to C.must D.need
13. Mr.Tom is in poor health.He_______be ill at any time.
A.may B.should C.can D.will
14. -Could I see you on Sunday?
-Yes,of course you_______.
A.can B.might C.will D.should
15. I thought you_______like something to read,so I have brought you some books.
A.may B.must C.could D.might
16. -Do you have to go out?
-Sorry,but I really_______.
A.have to B.must C.may D.can
17. “Manager,some people want to see you,_______they wait in the hall or outside?”asked the secretary.
A.will B.must C.shall D.may
18. There was plenty of time,she_______.
A.needn’t have hurried B.mustn’t have hurried
C.have hurried D.couldn’t have hurried
19. You_______walk for miles and miles among the hills without meeting anyone.
A.must B.need C.should D.may
20. You_______do what you like to the whole afternoon.
A.could B.can C.are able to D.can be able
21. Look,what you have done! You_______more careful.
A.may be B.had to C.should be D.would be
22. Whoever breaks the law_______.
A.can be punished B.is to punish
C.is to be punished D.are punished
23. Don’t throw the box away.It_______in the future.
A.shall be needed B.is needed C.might need D.might be needed
24. All that_______must be done.
A.should be done B.is done C.was done D.has been done
25. There_______an English evening next Saturday.
A.will have B.is going to be C.is to have D.is going to do
26. The news_______about everywhere now.
A.is talking B.has been talked
C.is being talked D.is being talking
27. We shall stay in the village for one or two days,and then we_______that mountain.
A.go to climb B.go on climbing
C.will have climbed D.are going to climb
28. Suddenly he thought that a bicycle_______be very useful.
A.would B.will C.is to D.should
29. Johnny,you_______play with the knife,you_______hurt yourself.
A.won’t;can’t B.mustn’t;may
C.shouldn’t;must D.can’t;shouldn’t
30. Your phone number again? I_______quite catch it.
A.couldn’t B.don’t C.didn’t D.can’t
31. Come early tomorrow,_______?
A.don’t you B.do you C.shall you D.will you
32. Let’s go to see our teacher who is in hospital,_______?
A.shall we B.will you C.don’t we D.do you
33. Everyone_______do his best to study well in order to sense the people well in future.
A.can B.should C.may D.might
34. -May I stop here?
-No,you_______.
A.might not B.needn’t C.mustn’t D.won’t
35. -Dare he go to the cinema in the evening?
-_______.
A.I dare too B.No,I don’t C.Yes,I do D.No,I daren’t
36. Don’t be worried.The news_______be true.
A.may not B.mustn’t C.needn’t D.shan’t
37. I will return your notes as soon as I_______copying them.
A.will finish B.do finish C.finish D.be finished
38. You_______do it even if you want to.
A.can’t B.have to C.mustn’t D.needn’t
39. When_______possible to get some more information?
A.has it B.had it C.would be it D.would it be
40. He_______the test,but he wasn’t careful enough.
A.could have passed B.was able to pass
C.might be able to pass D.must have passed
參考答案
1-10 ACCCB DCABA 11-20 DBCAD BCADB
21-30 CCDAB CDABC 31-40 DABCD ACBDA