GRAMMAR: MODAL VERBS (人教版高三英语下册教学论文)

发布时间:2016-4-17 编辑:互联网 手机版


Explanations and examples Practice exercises

Ability : can/ could/ be able to (=saying whether you are able to do something)

If you want to say whether someone is able to carry out an action, use can.

e.g. Guy can speak Russian.

When you put these sentences into the past tense, use could.

e.g. He was late for school because he couldn't find his bag.

Use could if there are conditions controlling whether the event will take place.

e.g. I could leave tomorrow, if I had the money.

In general, we use be able to when we talk about a specific achievement (particularly if it is difficult, requiring some effort) rather than a general ability. Here be able to means succeed in doing something or manage to do something.

e.g. He has now recovered from his injury and is able to drive again.

However, we commonly use can or could , even when are talking about specific occasions, with verbs of the senses, feel, hear, see, smell, taste, and verbs of “thinking”, believe, decide, remember, understand.

e.g. I can’t decide where to go for my holiday.

We don’t use be able to

when we talk about something that is happening as we are speaking:

before be + past participle:

e.g. This furniture can be assembled by anyone, with just a screwdriver.

We use be able to, not can or could, if the idea we want to express needs a to-infinitive, an-ing form, of a perfect tense, or if it follows another modal verb:

e.g. We were very lucky to be able to live in the country during our childhood.

We use will be able to, not can, to say that something will be possible in the future:

e.g. f the snow carries on like this, very few people will able to get to the concert.

have been able to do something to mean that someone has succeeded in doing something. could have done something to mean that someone was able to do something but did not do it.

can’t/ cannot to be unable to do something, because you do not have the ability, time equipment, etc; not be able to to be used mostly in past or future tenses. In the present tense, use can’t/ cannot. 1. Two eyes ………. see more than one. / The theatre ………. seat 2, 000 people.

2. Will you ………. come tonight? / ………. you come tonight?

3. I’m sorry I……….( answer) your letter yet.

4. Before liberation few workers………. support their families.

5. My students have taught me much, usually by asking questions that I ………. (not answer).

6. Jenny ………. leave the hospital only 6 hours after he baby was born.

7. The fire spread through the hotel very quickly but everyone ………. get out.

8. I ………. understand the speaker at all because what he said was beyond my understanding.

9. It was awful, not ………..see you for so long.

10. Since he left, none of the team members ………. match his enthusiasm.

11. We may ………. move some of the staff to a different department.

12. Antia ………. speak three languages before she was six.

13. When the new road is built, I ………. drive to work in under half an hour.

Keys: 1. can; can 2. be able to; can 3. haven’t been able to 4. could 5. couldn’t answer 6. was able to 7. was able to 8. could not 9. being able to 10. have been able to 11. be able to 12. could 13. will be able to

Permission: may/ might/ can/ could (=allowing someone to do something)

If you want to give or ask for permission, use can or may. May is more polite or formal than can.

e.g. You can leave when the bell rings.

Customers may purchase extra copies at half price.

Could is a polite way of asking for permission.

e.g. Could I leave early today?

Might is a very formal and old-fashioned way of asking for permission only.

e.g. Might I borrow your umbrella?

If we want to put extra pressure on someone to give a positive answer we can use can't or couldn't. For example, you might use couldn't where you expect that the answer is likely to be 'no', or where permission has been refused before:

e.g. Can't/Couldn't we stay just a little bit longer? Please?

To give and refuse permission we use can and can't:

e.g. No, you can't have another chocolate.

Notice that we prefer can/can't rather than could/couldn't to give or refuse permission.

We use can (for the present or the future) and could (for the past) to report permission.

e.g. Jim says that we can borrow his house as long as we leave it clean and tidy.

To report that in the past someone had general permission to do something, that is, to do it at any time, we can use either could or was/were allowed to. However, to report permission for one particular past action, we use was/were allowed to, but not could:

e.g. Last century, women were not allowed to/ couldn’t vote.

e.g. Although he didn't have a ticket, Ken was allowed to come in.

In negative sentences, we can use either couldn't or wasn't/weren't allowed to to report that permission was not given in general or particular situations:

e.g. We couldn't / weren't allowed to open the presents until Christmas.

If we use the present perfect, past perfect or an infinitive, we use be allowed to, not can/ could.

e.g. They have been allowed to keep the Roman coins they found in their garden. 1. He said we ………. use the car, too.

2. She is unlikely to ……….travel on that airline again.

3. ……….I come in?

4. This kind of thing……….(not ) happen.

5. ……….I trouble you with a question?

6. ---……….I smoke here?

--- No, you………./ Please don’t./ Yes, please.

7. You ………. take this seat if you like.

8. ----………. I ask for a photo of yours?

--- What did he say?

----He asked if he………. look at my photos?

9. --- So you mean I have been too strict with you?

--- Well, if you ………. say so.

10. Jim says we………. borrow his house as long as we leave it clean and tidy.

Keys: 1. can/could 2. be allowed to 3. may/ Can 4. can’t 5. May/ Might 6. Can, can’t/ May, mustn’t 7. may 8. can; could 9. may 10. could

Ask permission in these situations Use Can I …?, Could I…?, Can’t I…? or Couldn’t I…?

You want...

1. ……....another drink.

2………...leave your books with me. (be particularly polite)

3………..park your car on my drive. (I've already refused once)

Keys: 1. can 2. Could I 3. Can’t I /Couldn’t I

Possibility: can/ may/ could/ might (=saying whether something is possible)

Probability: should/ ought to (=saying whether something is likely)

Certainty: must (=saying that you are sure about something)

If you want to say that something is possible, use can or may. May is more polite or formal than can. If you want to suggest that the action is less likely to happen, use could or might. In affirmative sentences ( that is, sentences which are not questions or negatives), we use may or might to say there is a possibility of something happening or being true. There is often little difference in meaning, but might can suggest that there is less possibility. We can use could not can to express a similar meaning. We prefer could to show that we are giving an opinion about which we are unsure.

e.g. “Why isn’t Tim here yet?” “ It may/ might/ could be because his mother is ill again.”

e.g. We could go by bus.

e.g. We might go by bus. (=it is possible, but only if there are no problems)

However, when we make a decision now about something in the future, we use can.

e.g. You can go home when you’ve finished writing your composition.

We can use can in affirmative sentences when we talk about a more general possibility of something happening rather than the possibility of something happening in a particular situation.

e.g. The temperature can sometimes reach 35℃ in July.

e.g. Exceeding the stated dose may cause drowsiness. (from a medicine container)

We don’t use may to ask questions about the possibility of something happening. Instead we use, for example, could (n’t) or the phrase be likely. it is possible to use might in this type of question, but it is rather formal.:

e.g. Could it be that you don’t want to leave?

In negative sentences, including sentences with words like only, hardly or never, to say that something is not the case, we can use can’t (or more formally cannot) or couldn’t (or could not):

e.g. There can’t / couldn’t be any milk left-I would have seen it in the fridge.

We use may not or might not to say that it is possible that something is not true, and can’t or couldn’t to say that it is not possible that something is true.

e.g. There are plans to rebuild the town centre, but it may not/ might not happen for another years. ( It is possible that it won’t happen for another ten years.)

e.g. There are plans to rebuild the town centre, but it can not/ could not happen for another years. ( It is not possible that it will happen for another ten years.)

We use may well, might well or could well to say it is likely that something will happen:

e.g. The profits of the company may/ might/ could well reach $100 million this year.

We don’t use can well in this way to talk about the future. However, can well is used to talk about something we think or feel now:

e.g. I can well recall now how I felt when John told us he was moving to South Africa.

can/ may/ might/ could conceivably/ possibly to say it is possible that something will happen are conceivably and possibly.

If you want to suggest that an event is likely to happen, use should or ought to. It will probably take place, but you are not completely sure.

e.g. We ought to be there by 6 o'clock.

If you want to say that you are sure something is true, use must.

e.g. You must be tired, after all your hard work.

To express the opposite meaning (=you are sure something is not true) use can't.

e.g. You can't be that tired, you've only been working for an hour.

For the past, we use must have done and the negative form is couldn’t have done. 1. There ………. be some cake left. I’ll go and look.

2. Mountain daisies ………. be yellow or red.

3. It ………. rain later.

4. ……… you ……. be visiting Greece again this summer?

5. There ………. hardly be any doubt that he was guilty.

6. A wise man ……make mistakes/ You …… be right.

7. It’s nearly 7 o’clock. Jack……be here at any moment.

8. This pen looks very mine. Yet it isn’t . Whose…… it be?

9. He…… not be there today, but I’m not quite sure.

10. ---When can I come for the photos? I need them tomorrow afternoon.

--- They…… be ready by 12:00.

11. ---There is a lot of smoke coming out of the house over there.

--- Really? It…… be a fire, most probably.

12. ---Why didn’t you answer my phone call? ---Well, I ……(sleep), so I didn’t hear it.

13. --- I heard they went skating in the mountains last winter.

--- It…… true because there was little snow there.

14. Our house is on the top of the hill, and in winter the winds……be pretty cold.

15. --- I feel the house shaking.

--- So do I. It …… be a sign of earthquake probably. Let’s hurry to leave here.

Keys: 1. may/ might/ could 2. can 3. may’ might/ could 4. Are, likely to 5. can/ could 6. can, may 7. should/ ought to 8. can 9. may 10. should/ ought to 11. should/ ought to 12. must have been sleeping 13. couldn’t have been 14. can 15. should

Where necessary, suggest a correction for these sentences, or put a√.

1. I think I saw her go out, so she mightn't be at home.

2. It mightn't be true. There must be some mistake.

3. It's snowing heavily in Scotland so it can take Hugh a long time to get here.

4. If we don't get to the market soon they can't have any flowers left. They will all have been old.

5. If you're free at the moment, we may have a job for you.

6. May you be given the job permanently?

7. I thought they were on holiday-- but I can be wrong, of course.

8. I might go out later if the weather improves.

9. Children may enter only when accompanied by an adult.

Keys: 1. √ 2. It couldn’t / can’t be true 3. it may/ might/ could take 4. they may not/ might not have 5. √ 6. Could you be given..; Could it be that you’ll be give…; Are you likely to be given..; Might you be given … 7. I nay/ might be wrong 8. √ 9. √

Suggestions/ request/ offers/ invitations: had better/ should/ shall/ can/ could/ may/ might/ will/ would

Had better ( I’d better/ you’d better, etc.)

I’d better do something = it is advisable to do it. If don’t, there will be a problem or a danger:

e.g. I have to meet Ann in ten minutes. I’d better go now or I’ll be late.

The negative is I’d better not.

You can use had better when you warn somebody that they must do something.

e.g. You’d better be on time. ( or I’ll be very angry.)

Had better is similar to should but not exactly the same. We use had better only for a particular situation ( not for things in general). You can use should in all types of situation to give an opinion or to give advice. Also, with had better, there is always a danger or a problem if you don’t follow the advice. Should only means “it is a good thing to do.”

We often use can or could to ask people to do things (Can you…?/ Could you…?) Note that we say “ Do you think (you) could …?” not can.

We also use will and would to ask people to do things ( but can and could are more usual) “Would you please…?/ Would you like…?/ Would you mind…?/ Will you please…?”

To ask for something we use Can I have …? or Could I have…?/ May I have…?

To offer to do something, we sometimes use Can I…? You can also use I’ll… to offer to do things.

e.g. You look tired. I’ll get you a cup of tea. 1. I have an appointment in ten minutes. I………. go now or I’ll be late.

2. It’s a great film. You ………. go and see it. You’ll really like it.

3. I think all drivers ………. wear seat belts.

4. Do you think you ………. lend me some money until next week?

5. …… you please be quiet? I’m trying to concentrate.

6. ( in a shop) …….. these postcards, please?

7. ( on the phone) Hello, …….. I speak to Tom , please?

8. ........ I help you?/ …… I get you a cup of coffee?

9. ……. I have some bananas? --- No, you can’t.

10. I ……. like to have a talk with you.

11. If you want help. Let me know, …….. you?

12. …….. you mind my opening the window?

13. ……… I fetch some water for you or ………. you do it yourself?

Keys: 1. had better 2. should 3. should 4. could 5. Would 6. Can I have/ Could I have 7. Can/ could/ may 8. Can/ can 9. May 10. would/ should 11. will 12. Would 13. Can , will

Necessity: must/ have to (=saying that something is necessary)

If you want to say that it is necessary for something to happen, use must or have (got ) to .

If you want to express the opposite meaning (=it is unnecessary for something to happen) use needn't/need not / not need to or don’t have to .

e.g. I must get my hair cut this weekend.

e.g. There’s plenty of time so you needn't worry.

When we want to say that it will be necessary for someone in the future, we use must, have ( got) to, or will have to.

Have (got) to is less formal than the others, and is particularly common in spoken English. We can often use need (to) with a similar meaning.

Using have (got) to suggests that someone else or some outside circumstances or authority makes something necessary. We use must when the speaker decides it is necessary.

We normally use must, not have (got) to, when we conclude that something (has) happened or that something is true.

e.g. The hall’s packed. There must be about 2,000 people at the meeting.

However, in informal speech, we can use have (got) to. When we give a negative conclusion we rarely use either must not or hasn’t/ haven’t got to. Instead we use can’t /cannot/ couldn’t:

e.g. “I’m seeing Dr Evans next week.” “That can’t be right. He’s on holiday then.”

Must has no other forms than the present tense (no past tense, no participles, etc.) and in past tense sentences which say that it was necessary to do something, we use had to instead. To draw a conclusion about something in the past, we use must have done.

Sometimes we can use either have to or have got to. However, we prefer have to with frequency adverbs such as always, never, normally, rarely, sometimes, etc.

Need can be used as a modal verb (before a bare infinitive) or as an ordinary verb.

e.g. You needn't speak so loudly. (= modal verb)

e.g. She's thirsty. She needs a drink. (= ordinary verb)

When it is a modal verb need is most commonly used in negative sentences, although it is sometimes also used in questions:

e.g. Need you go home so soon? (or, more commonly Do you have to go...?)

Compare these uses of needn’t and don’t need to.

To give permission not to do something we can use either needn't or don't need to: You needn't cut the grass, I'll do it later. √

You don't need to cut the grass, I'll do it later. √

To talk about a general necessity, we prefer don't need to: You don't need to be over 18 to get into a disco. √

You needn’t be over 18 to get into a disco. ×

When we say that it was not necessary to do something in the past, and it wasn't done, we use didn't need to or didn't have to. To show that we think something that was done was not, in fact, necessary we use need not have:

e.g. Chris and June phoned to say that they couldn't come to eat, so I didn't need/have to cook dinner. (=I didn't cook the dinner)

e.g. I needn't have cooked dinner. Just as it was ready, Chris and June phoned to say that they couldn't come to eat. (= I did cook the dinner) Complete these sentences with a form of have to or must (whichever is more likely) + an appropriate verb.

1. He's got a lung problem and he ...................... to hospital every two weeks.

2. You ...................... and visit us soon. It would be so nice to see you again.

3. That's really good news. I ...................... my friend, Steve.

4. I always sleep through the alarm clock. My Dad ...................... me every morning.

5. As I won't be at home tonight, I ...................... my homework during my lunch break.

6. “Can we meet on Thursday morning?” “Sorry, no. I ...................... to the dentist at 11:00.”

7. I'm feeling really unfit. I ...................... more exercise.

8. She…………come with us if she doesn't want to.

9. Jim and Bob are here. They say they ……………see you urgently.

10. I bought a new car last year, and then a month later I won one in a competition. So I …….. (spend) all that money.

11. I …….. (have) an interview. They accepted me without one.

Keys: 1. have to go 2. must come 3. must tell 4. has to wake 5. have to do 6. have to go 7. must take/ do 8. needn't 9. need to 10. needn’t have spent 11. didn’t need to have

Match the sentence beginnings and ends.

1. You mustn't drink alcohol a. to enjoy it.

2. You mustn't keep medicines b. when you go into a pub.

3. You don't have to be a member c. if teachers object to the new curriculum.

4. You don't have to play golf well d. to run up and down the aisle of the aircraft.

5. Newspapers mustn't e. to use the tennis club.

6. You don't have to drink alcohol f. when you drive.

7. Newspapers don't have to say g. who provided their information.

8. Children mustn't be allowed h. where children can get them.

9. You mustn't be surprised i. mislead the public.

Keys: 1+f 2+h 3+e 4+a 5+I 6+b 7+g 8+d 9+ c

Obligation: must/ should (=saying what someone must do)

If you want to demand that something happens, or that someone does something (=to express obligation), use must. You can also use this idea about yourself, in order to express a sense of duty. Only use must not/ mustn’t in present tense. When talking about past, use couldn’t or wasn’t/ weren’t allowed to; when talking about the future use will not be allowed to. must not/ mustn’t to tell or order someone not to do something. Can’t to say that someone is not allowed to do something.

e.g. The builders must finish the job today.

e.g. I’m sorry. You know I can’t discuss my work-it’s secret.

e.g. This book must not be removed from the library.

We can often use should or ought to when we talk about obligation.

* Giving ADVICE or making a RECOMMENDATION:

e.g. “This soup is too salty!” “You should / ought to send it back.”

However, we use should (or would), not ought to, when we give advice with I:

* Talking about a RESPONSIBILITY or DUTY:

e.g. People should / ought to be warned of the danger of swimming off this beach.

We use should / ought to + have + past participle to talk about an obligation in the past. We often indicate some criticism or regret:

e.g. He should / ought to have asked me before he took my bike. (I'm annoyed)

We also use should / ought to + have + past participle to talk about an expectation that something happened, has happened, or will happen:

e.g. If the flight was on time, he should / ought to have arrived in Jakarta early this morning.

We often use should with I think/ I don’t think/ Do you think….?

We also use should when something is not right or what we expect.

e.g. I wonder where Liz is. She should be here by now.(= she isn’t here yet, and this is not normal)

We can use (be) supposed to instead of should / ought to to talk about an obligation to do something. It is commonly used in spoken English to express a less strong obligation:

e.g. I'm supposed to be there at 10.00.

e.g. The work was supposed to start last week.

We use (be) supposed to when we report what many people think is true:

e.g. Eating sweets is supposed to be bad for your teeth. (not ...should be bad for...) 1. We ……….. leave the house before 6 o'clock.

2. I ………….remember to bring my notebook.

3. You'll catch cold if you go out like that. I think you ………take a hat.

4. I ……..leave early tomorrow, if I were you.

5. I ………….visit my parents more often.

6. We ……..(take) a taxi when it rained. (I'm sorry we didn't)

7. “Do You think I ….. apply for this job?” “ Yes, I think we ………..”

8. The price on this packet is wrong. It … $ 1.20, not $ 1.50.

Keys: 1. mustn't 2. must 3. should / ought to 4. should/ I would leave/I'd leave... 5. should / ought to 6. should / ought to have taken 7. should, should 8. should

Habits: will/ would/ used to

We can use will (for the present) and would (for the past) to talk about characteristic behavior or habits, or about things that are or were always true:

e.g. Every day Dan will come home from work and turn on the TV.

We don't use would in this way to talk about a particular occasion in the past.

e.g. Each time I gave him a problem he would solve it for me.

e.g. Last night I gave him a problem and he solved it for me. (not ...he would solve it...)

In speech, we can stress will or would to criticise people's characteristic behaviour or habits:

e.g. She will leave all the lights on in the house when she goes out.

If we want to talk about things that happened repeatedly in the past, but don't happen now, we can use would or used to + infinitive. Used to is more common in informal English:

e.g. We would / used to lend him money when he was unemployed.

We use used to but not would when we talk about past states that have changed:

e.g. The factory used to be in the city centre.

When we use would we need to mention a specific time or set of occasions.

e.g. We used to play in the garden. (not We would play...)

e.g. Whenever we went to my Uncle Frank's house, we would / used to play in the garden.

We don't use either used to or would when we say exactly how many times something happened, how long something took, or that something happened at a particular time:

e.g. We visited Switzerland four times during the 1970s.

Study how we normally make questions and negatives with used to in spoken English:

e.g. Did your children use to sleep well when they were babies?

e.g. I didn't use to like visiting the dentist when I was young.

These forms are sometimes written as ...did ... used to... and '...didn't used to...', but some people think this is incorrect. However, in more formal spoken and written English the following negative and question forms are also used, although this question form is now rare:

e.g. There used not to be so much traffic. (more likely is There didn't use to be...)

e.g. Used you to go to university with the Evans brothers? (more likely is Did you use to...?)

Notice that nowadays very few people use used to in tags:

e.g. He used to play cricket for Australia, didn't he? (rather than ..., usedn't he?)

1. During the war, people ……… all kinds of things that we don't eat now.

2. A baby…………. recognise its mother's voice soon after it is born.

3. Early passenger planes …………. hold more than 30 passengers.

4. I was happy when Sam left. He………. talk about people behind their backs.

5. I ………smoke heavily when I was at university.

6. I………like going to pop concerts when I was a teenager.

7. Business people ............. watch what their competitors are doing with great interest.

8. The country now known as Myanmar ..................... be called Burma.

9. My father didn't know that we ..................... borrow the car when he was at work.

10. When I was a child, summers .................. be warmer and winters colder than now.

11. Accidents ................ happen in the home, however safe we try to make them.

12. When the weather was good, we ................... go walking in the hills every weekend.

Keys: 1. would 2. will 3. wouldn't 4. would 5. used to 6. used to 7. will 8. used to 9. would/ used to 10. used to 11. will 12. would/ used to

Willingness: will/ would

We use will (or '11) when we talk about WILLINGNESS to do something (e.g. in offers, invitations, requests, and orders) and will not (or won't) when we talk about UNWILLINGNESS to do something (e.g. reluctance, refusal):

e.g. I'll give you another opportunity to get the correct answer.

e.g. Mum! Sue won't give me back my pencil case.

Notice that we can also talk about the refusal of a thing to work in the way it should:

e.g. The top won't come off. / The key won't fit the lock.

To talk about general or repeated willingness in the past we can sometimes use would, but we can't use would in this way to talk about a particular occasion in the past. However, we can use would not either when we talk about unwillingness in general or about a particular occasion.

e.g. We thought that people wouldn't / would buy the book. (= general)

e.g. She wouldn't say what was wrong when I asked. (not ...would say...) (= particular occasion) Correct the sentences if necessary, or put √.

1. I had to work late on Friday, so my mother would pick up Sue from school.

2. Mary wouldn't sing for me, even though I often asked her to.

3. The moment I asked Steve, he would agree to lend me the car for the day.

4. When I phoned, the receptionist wouldn't let me have an appointment with Dr Johnson before next week.

5. At the interview they wouldn't tell me how much travelling was involved in the job.

6. Yesterday he would make me sandwiches and would bring me a cup of coffee.

7. When I had problems with my homework last night, my father would do it for me.

8. Five years ago, the children in this school would help to plant all the trees you see before you.

9. Before he moved to London, Thomas would meet me every day after work.

10. When I was young, shopkeepers would cycle around town, delivering food to customers.

Keys: 2. √3. agreed 4. √5. √ 6. made; brought 7. did 8. helped 9. √10. √

Intention: will/ shall (=saying what you are going to do)

If you want to say that you intend to do something, use will or shall. You can emphasize the meaning of intention if you say the modal louder than the surrounding words.

Shall is only used with the first person (I or we), and is much less common than will. It is hardly ever used in American English.

e.g. This letter says they will definitely give us our money back.

e.g. I shan't stay long.

To express an intention at a time in the past, use would.

e.g. I tried to explain, but nobody would listen.

Use would if there are conditions controlling whether something will take place.

e.g. I would leave tomorrow, if I had the money.

Prediction: will/ shall (=saying what you think is going to happen)

If you want to say that something is certain to happen, use either will or shall. As with the other uses of these words, shall tends to be found only with the first person (I or we), and is much less common than will. Shall is very rare in American English.

e.g. The cars will be there on time, I promise.

e.g. There is no doubt that we shall win.

I / you / he (etc) must

can’t be (tired/ hungry/ at work. etc.)

be (doing/ coming/ joking etc.)

do/ go/ know/ have etc.

We use must to say that we feel sure something is true. We use can’t to say that we feel something is not possible. For the past we use must have (done) and can’t have (done).

I / you / he (etc) must

can’t have been (asleep/ at work. etc.)

been (doing/ working etc.)

done/ gone/ known/ had etc.

We use could have done for things which were possible but did not happen.

I / you / he (etc) may

might (not) be (true/ in his office etc.)

be (doing / working/ having etc.)

do/ know/ have/ want etc.

We use may or might to say that something is a possibility. The negative forms are may not and might not. For the past tense we use may have (done) or might have (done):

I / you / he (etc) may

might (not) have been (asleep/ at home etc.)

been (doing / waiting etc.)

done/ known/ had/ seen etc.

When we want to show we did something but now we know that it was not necessary, we can use needn’t have done.

We use should / ought to + have + past participle to talk about an obligation in the past. We often indicate some criticism or regret