情态动词英文版讲解.doc

GRAMMAR: MODAL VERBSExplanations and examplesPractice exercisesAbility : 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 couldnt 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 cant decide where to go for my holiday.We dont use be able tol when we talk about something that is happening as we are speaking:l 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.cant/ 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 cant/ cannot.1. Two eyes . see more than one. / The theatre . seat 2, 000 people.2. Will you . come tonight? / . you come tonight?3. Im 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. havent been able to 4. could 5. couldnt 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 toPermission: 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 cant or couldnt. For example, you might use couldnt where you expect that the answer is likely to be no, or where permission has been refused before: e.g. Cant/Couldnt we stay just a little bit longer? Please? To give and refuse permission we use can and cant: e.g. No, you cant have another chocolate. Notice that we prefer can/cant rather than could/couldnt 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/ couldnt vote. e.g. Although he didnt have a ticket, Ken was allowed to come in. In negative sentences, we can use either couldnt or wasnt/werent allowed to to report that permission was not given in general or particular situations:e.g. We couldnt / werent 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 dont./ 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. cant 5. May/ Might 6. Can, cant/ May, mustnt 7. may 8. can; could 9. may 10. could Ask permission in these situations Use Can I ?, Could I?, Cant I? or Couldnt I? You want.1. .another drink. 2.leave your books with me. (be particularly polite)3.park your car on my drive. (Ive already refused once)Keys: 1. can 2. Could I 3. Cant I /Couldnt 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 isnt 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 youve 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 dont use may to ask questions about the possibility of something happening. Instead we use, for example, could (nt) 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 dont 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 cant (or more formally cannot) or couldnt (or could not):e.g. There cant / couldnt be any milk leftI 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 cant or couldnt 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 wont 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 dont 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 oclock.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 cant. e.g. You cant be that tired, youve only been working for an hour. For the past, we use must have done and the negative form is couldnt have done.1. There . be some cake left. Ill 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. Its nearly 7 oclock. Jackbe here at any moment.8. This pen looks very mine. Yet it isnt . Whose it be?9. He not be there today, but Im 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 didnt you answer my phone call? -Well, I (sleep), so I didnt 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 windsbe pretty cold.15. - I feel the house shaking.- So do I. It be a sign of earthquake probably. Lets 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. couldnt have been 14. can 15. shouldWhere necessary, suggest a correction for these sentences, or put a.1. I think I saw her go out, so she mightnt be at home.2. It mightnt be true. There must be some mistake.3. Its snowing heavily in Scotland so it can take Hugh a long time to get here.4. If we dont get to the market soon they cant have any flowers left. They will all have been old.5. If youre 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 couldnt / cant 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 youll 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 ( Id better/ youd better, etc.) Id better do something = it is advisable to do it. If dont, there will be a problem or a danger: e.g. I have to meet Ann in ten minutes. Id better go now or Ill be late. The negative is Id better not. You can use had better when you warn somebody that they must do something. e.g. Youd better be on time. ( or Ill 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 dont 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 Ill to offer to do things. e.g. You look tired. Ill get you a cup of tea.1. I have an appointment in ten minutes. I. go now or Ill be late. 2. Its a great film. You . go and see it. Youll 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? Im 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 cant.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 neednt/need not / not need to or dont have to .e.g. I must get my hair cut this weekend.e.g. Theres plenty of time so you neednt 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 halls 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 hasnt/ havent got to. Instead we use cant /cannot/ couldnt:e.g. “Im seeing Dr Evans next week.” “That cant be right. Hes 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 neednt speak so loudly. (= modal verb)e.g. Shes 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 neednt and dont need to.To give permission not to do something we can use either neednt or dont need to:l You neednt cut the grass, Ill do it later. l You dont need to cut the grass, Ill do it later. To talk about a general necessity, we prefer dont need to:l You dont need to be over 18 to get into a disco. l You neednt be over 18 to get into a disco. When we say that it was not necessary to do something in the past, and it wasnt done, we use didnt need to or didnt 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 couldnt come to eat, so I didnt need/have to cook dinner. (=I didnt cook the dinner)e.g. I neednt have cooked dinner. Just as it was ready, Chris and June phoned to say that they couldnt 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. Hes 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. Thats really good news. I . my friend, Steve.4. I always sleep through