1、1 比较 can 和 be able to 1）can/could 表示能力；可能 （过去时用 could）, 只用于现在式和过去式（ could） 。be able to 可以用于各种时态。例如： They will be able to tell you the news soon. 他很快就能告诉你消息了。 表示成功地做了某事时，用 was/were able to，不能用 could。例如： He was able to flee Europe before the war broke out. = He managed to flee Europe before the war br
2、oke out. 2）提出委婉的请求， （注意在回答中不可用 could） 。例如： - Could I have the television on? 我能看电视吗？ - Yes, you can. / No, you cant. 可以/ 不可以。 3）在否定句、疑问句中表示推测或怀疑。例如： He couldnt be a bad man. 他不大可能是坏人。Could he help us ?The girl couldnt have stolen your electronic dictionary . 4） 有时会，he can be difficult to get along w
3、ith , even though he is good 5） 否定推测用 cant。例如： If Tom didnt leave here until five oclock, he cant be home yet. 如果汤姆五点才离开这儿，他此时一定还未到家。 2 比较 may 和 might 1） 表示允许或请求；表示没有把握的推测；may 放在句首，表示祝愿。例如： May God bless you! 愿上帝保佑你！ He might be at home. 他可能在家。 注意：might 表示推测时，不表示时态，只是可能性比 may 小。 2） 成语：may/might as w
4、ell，后面接不带 to 的不定式，意为 “不妨“。例如： If that is the case, we may as well try.如果情况确实如此，我们不妨试一试。 典型例题 Peter _come with us tonight, but he isnt very sure yet. A. must B. may C. can D. will 3 have to 1)have to 表示客观的需要，must 表示说话人主观上的看法，既主观上的必要。例如： My brother was very ill, so I had to call the doctor in the midd
5、le of the night. 弟弟病得很厉害，我只得半夜里把医生请来。 （客观上需要做这件事） He said that they must work hard. 他说他们必须努力工作。 （主观上要做这件事）2） have to 有人称、数、时态的变化，而 must 只有一种形式。但 must 可用于间接引语中表示过去的必要或义务。例如： He had to look after his sister yesterday. 他昨晚只得照顾他姐姐。 3） 否定结构中：dont have to 表示“不必”，mustnt 表示“禁止”。例如： You dont have to tell him
6、 about it. 你不一定要把此事告诉他。 You mustnt tell him about it. 4 must Must you make a noise in the classroom? 1） must 用在肯定句中表示较有把握的推测，意为“一定“。 2） must 表对现在的状态或现在正发生的事情的推测时，must 后面通常接系动词 be 的原形或行为动词的进行式。例如： You have worked hard all day. You must be tired. 你辛苦干一整天，一定累了。（对现在情况的推测判断） He must be working in his off
7、ice. 他一定在办公室工作呢。 3） must 表示对已发生的事情的推测时，must 要接完成式。例如： I didnt hear the phone. I must have been asleep. 我刚才没有听到电话，我想必是睡着了。 4） must 表示对过去某时正发生的事情的推测，must 后面要接不定式的完成进行式。例如： -Why didnt you answer my phone call? 为何不接我的电话？ -Well, I must have been sleeping, so I didnt hear it.唉，肯定在睡觉，所以没有听见。 5) At this mom
8、ent, our teacher must be correcting our exam papers. 这时，想必我们老师正在批改试卷。 情态动词+ 动词现在进行时，表示对现在或将来正在进行的情况进行推测。 1）情态动词+动词完成时，表示对过去情况的推测。例如： The road is wet. It must have rained last night. 地是湿的，昨天晚上一定下雨了。 2）情态动词+动词的现在完成进行时，表示对过去正在发生事情的推测。例如： Your mother must have been looking for you. 你妈妈一定一直在找你。 3）推测的否定形式
9、，疑问形式用 cant, couldnt 表示。例如： Mike cant have found his car, for he came to work by bus this morning. 迈克一定还没有找回他的车，因为早上他是坐公共汽车来上班的。 may（might） have + done sth, can （could ） have + done sth 表示过去，推测过去时间里可能发生的事情。例如： Philip may （might ） have been hurt seriously in the car accident. 菲力浦可能在车祸中受了重伤。 Philip ca
10、n （could ） have passed the exam but he didnt study hard 4） must have +done sth，对过去时间里可能发生的事情的推测，语气较强，具有“肯定“，“谅必“的意思。例如： -Linda has gone to work, but her bicycle is still here. 琳达已经去上班了，但她的单车还在这儿。 -She must have gone by bus.肯定乘巴士去的。 5)ought to have done sth, should have done sth 表示本应该做某事，而事实上并没有做。否定句
11、表示“不该做某事而做了”。例如： You ought to （should） have been more careful in this experiment. 你当时在做试验时应该更仔细点。 He ought not to have thrown the old clothes away.他不该把旧衣服扔了。 （事实上已扔了。 ） ought to 在语气上比 should 要强 It is strange that he should have spoken to his teacher in this way . 6） neednt have done sth 表示本没必要做某事，但做
12、了。例如： I dressed very warmly for the trip, but I neednt have done so. The weather was hot. 旅行时，我衣服穿得较多，其实没有必要。那时天很热。 7） would like to have done sth 表示本打算做某事，但没做。例如： I would like to have read the article, but I was very busy then. 我想读这篇文章，但太忙了一直没读。 should 和 ought to 除了上述的用法，两者还可表示“想必一定，按理应该”的意思。例如： I
13、ought to be able to live on my salary. 靠我的薪水，想必也能维持了。 It ought to be ready now. 想必现在准备好了吧。 They should be there by now, I think. 现在他们该到那儿了。 The poems should be out in a month at most. 诗集估计最多还有一个月就要出版 Dont worry . I have sent an ambulance to you .They should be there any second would rather do would
14、rather not do would rather than 宁愿 而不愿。 还有 would sooner, had rather, had sooner 都表示“宁愿”、“宁可”的意思。例如：If I have a choice, I had sooner not continue my studies at this school. 如果有选择的余地，我宁可辍学离开这个学校。 I would rather stay here than go home. = I would stay here rather than go home. 我宁愿呆在这儿，而不愿回家。 典型例题 -Shall
15、 we go skating or stay at home? -Which _ do? A. do you rather B. would you rather C. will you rather D. should you rather 答案 B。 I would rather you put your heart into your studies 。 1）-Could I borrow your dictionary? -Yes, of course, you_. A. might B. will C. can D. should 2）-Shall I tell John about
16、 it? -No, you _. Ive told him already. A. neednt B. wouldnt C. mustnt D. shouldnt 3）-Dont forget to come to my birthday party tomorrow. -_. A. I dont B. I wont C. I cant D. I havent 比较 need 和 dare 这两词既可做实义动词用，又可做情态动词用。作为情态动词，两者都只能用于疑问句，否定句和条件句。need 作实义动词时后面的不定式必须带 to，而 dare作实义动词用时, 后面的 to 时常可以被省略。 1
17、） 实义动词：need（需要, 要求） need + n. / to do sth /doing 2） 情态动词：need，只用原形 need 后加 do，否定形式为 need not。例如： Need you go yet? 你要走了吗？ Yes, I must. / No, I neednt.是的，我要走了/ 不，不急着走。 Dare / dare not Dare you go out alone at night ? No , I dare not . I didnt know whether you dared say that to the teacher . 其他用法 1 can
18、not but choose =have to I cannot but choose to go. 2 can never enough / cant too much I cant thank you too much . You can never be careful when crossing the street .专项练习1-No one _ be compared with Yao Ming in playing basketball.-Oh, you are really his big fan.A can B need C must D might2. It _ be th
19、e postman at the door. Its only six oclock.A mustnt B cant C wont D neednt 3. The police still havent found the lost child, but theyre doing all they_.A can B may C must D should4. I left my handbag on the train, but luckily someone gave it to a railway official.-How unbelievable to get it back! I m
20、ean, someone_ it.A will have stolen B might have stolenC should have stolen D must have stolen5 Although this _sound like a simple task, great care is needed.A must B may C shall D should6 If you _ go, at least wait until the storm is over.A can B may C must D will7 You _ park here! Its an emergency
21、 exit.A wouldnt B neednt C couldnt D mustnt 8 You _ buy a gift, but you can if you want to.A must B mustnt C have to D dont have to 9 As you know, although there are no classes on weekends now, no students_ go out of the school without the headmasters permission.A will B must C may D shall10 They _
22、have arrived at lunchtime but their flight was delayed.A will B can C must D should11 Why didnt you come to Simons party last night?-I wanted to, but my mom simply_ not let me out so late night.A could B might C would D should12 Theres no light onthey_ be at home.A cant B mustnt C neednt D shouldnt
23、13 Tom came to work last Friday, but no one has seen him since.-_ he have had an accident?A Should B Must C Might D Could14 Shall I inform him of the change of the schedule right now?-I am afraid you _, in case he comes late for the meetingA will B must C may D can15 Liza_ well not want to go on the
24、 trip- she hates travelling.A will B can C must D may16 Some people who dont like to talk much are not necessarily shy; they_ just be quiet people.A must B may C should D would17 John, look at the time._ you play the piano at such a late hour?A Must B Cant C May D Need18 You_ scold such a pupil who
25、always keeps silent so seriously that you _ hurt him.A should; can B may; will C mustnt; may D cant; must19 Doctors say that exercise is important for health, but it_ be regular exercise.A can B will C must D may20 “ You_ have a wrong number,” she said.“ Theres no one of that name here.”A need B can
26、 C must D would21 We _ Johns name on the race list yesterday but for his recent injury.A will put B will have put C would put D would have put22 May I take this book out of the reading room?-No, you_. You read it in here.A mightnt B wont C neednt D mustnt 23What do you think we can do for our aged p
27、arents?- You _ do anything except to be with them and be yourself.A dont have to B ought to C mustnt D cant24. I _ have watched that movie-itll give me horrible dreams.A shouldnt B neednt C couldnt D mustnt25 I dont care what people think.-Well, you_.A could B would C should D might26 My uncle was p
28、oor but liked fashion, so he_ dress up as a rich man.A could B would C should D might27 He must have finished his homework last night,_ he?A mustnt B didnt C neednt D hasnt28 I cant leave. She told me that I _ stay here until she comes back.A can B must C will D may29 A left-luggage office is a plac
29、e where bags_ be left for a short time, especially at a railway station.A should B can C must D will30 The traffic is heavy these days. I _ arrive a bit late, so could you save me a place?A can B must C need D might31 There_ be any difficulty passing the road test since you have practiced a lot in the driving school.A mustnt B shant C shouldnt D neednt
