九年级英语unit 8 语法（情态动词）情态动词：情态动词有具体的词义；情态动词没有人称和数的变化；情态动词后必须加上动词原形；情态动词同助动词一样，需要与其他词语一起构成句子的谓语。
can：1、表示能力，意为“能会”；2、表示请求，允许，意为“可以”；3、表示推测，意为“可能”。
could：1、can 的过去式，意为“能、会”，表示过去的能力2、在疑问句中表示委婉请求may：1、表示请求、许可，意为“可以”2、表示推测，常用于肯定句中，意为“可能、也许”might：1、may的过去式2、表示推测，常用于肯定句中，意为“ 可能、也许”must：1、表示主观看法，意为“必须、应该”2、表示有把握的推测，用语肯定句need：1、表示需要、必须，主要用于否定句和疑问句中should：1、意为“ 应该”，表示要求和命令 2、表示劝告、建议had better：意为“最好”，表示建议（一） can 的用法1.表示能力（体力、知识、技能）。
Can you lift this heavy boxMary can speak three languages.Can you skateCan只有一般现在时和一般过去式；而be able to可以用于任何时态时态。
I’ll not be able to come this afternoon.当表示“经过努力才得以做成功某事”时应用be able to，不能用Can。
He was able to go to the party yesterday evening in spite of the heavy rain.2.表示请求和允许, 此时可与may互换。
在疑问句中还可用could, might 代替，不是过去式，只是语气更委婉。
(1).---Can I go now --- Yes, you can. / No, you can’t.(2).--- Could I come to see you tomorrow --- Yes, you can. ( No, I’m afraid not. )3.表推测可能性。
Someone is knocking at the door, and who can it beIt can’t be Tom because he has gone to Beijing.（二）、could的用法1、can的过去式，意为“ 能、会” ，表示过去的能力。
He could write poems when he was 10.2、 could 在疑问句中，表示委婉的语气，此时 could 没有过去式的意思。
---Could I use your pen ---Yes, you can.（三）、 may的用法1、表示请求、许可，比can 正式。
May I borrow your bike You may go home now.2、表示推测，谈论可能性，意为“ 可能，或许”。
It may rain tomorrow . She may be at home.3、 may的过去式为might ，表示推测时。
可能性低于may 。
He is away from school. He might be sick.（四）、 must的用法1、must 表示主观看法，意为“必须、一定”。
You must stay here until I come back.Must I hand in my homework right now2、must否定形式mustn’t表示“ 一定不要、千万别、禁止, 不许”。
You mustn’t play with fire.Y ou mustn’t be late.3、以must开头的一般疑问句，肯定回答用must，否定回答用needn’t或don’t have to 。
---Must I finish my homework ---No, you needn’t.4、must 一定，表示有把握的推测，用于肯定句中。
The light is on, so he must be at home now.（五）、need的用法1、need 作情态动词时，情态动词+V原（以need开头的一般疑问句，肯定回答用must，否定回答用needn’t或don’t have to 。
---Need I stay here any longer ---Yes, you must. ---No. you needn’t .2、need作实义动词时，有人称、数和时态的变化。
当主语是人时用need to do sth,当主语是物时用need doing sth.I need to do it right now. He needs to learn more about the girl.（六）、dare 的用法(敢、敢于)1、dare 作为情态动词，无第三人称单数形式，只有一般现在时和一般过去时。
Dare he tell them what he knows2、dare 作为实义动词(dare to do sth)，此时有人称、数及时态的变化。
He doesn’t dare to break his promise.（七）、should的用法1、should 意为“应该” ，可表示劝告、建议、义务、责任等。
We should protect the environment.2、Should have done 表示对过去动作的责备、批评。
You should have finished your homework.（八）、had better 的用法(最好，没有人称的变化)had better (not)do sthWe had better go now. You had better not give the book to him.表示推测含义的情态动词：must 一定>can可能>could可能>may可能>might可能>may not可能不>can’t不可能go to the cinema, mum---C ertainly, but you ________ be back by 11 o’clock.A. canB. mayC. mustD. need______ get there by bus.A. don’t needB. needn’t toC. don’t need toD. need don’t to_______ worry about me. It’s nothing serious.A. can’tB. mustn’tC. needn’tD. won’t4. The man in the office be Mr. Black because he went home just now.’t not ’t’tyou go surfing with us this afternoon---I’d like to , but I look after my sister at home , because my mother is ill.toI take this book out of the reading room--- .Pease read it here.A. Certainly , you needn’t, you mustn’t , you may notWhere is Mary --- She in the library.be be be have beenroom is dark. He must to bed.going gone been goneyour father stay home tonight ---I’m not sure, He to work.go go be gone be goingis Tom ---He isn’t here I think he have gone home.or B or C11 .---I think Helen is at home.---No, she be at home, for she phoned me from the airport just five minutes ago.’t ’t’t ’t12. He’s late. What have happened to him\ \he be watching TV now---Yes, he be watching TV now.---No, he _____ be watching TV now.”A. Must; can; mustn’tB. Can; must; can’tC. Must; must; can’tD. Can; can; mustn’t14. You must be a writer, you’t ’t15. You must have seen her yesterday, you’t ’t’t ’t16. You must have seen her, you’t ’t’t or Bhave come here yesterday, but he didn’t.A. couldB. shouldC. ought toD. A or B or Che do it ---No, he .A. mustn’tB. needn’tC. doesn’t have toD. B or Cyou go now ---Yes, I . ---No, I .A. need; needn’tB. must; needn’tC. may; mustn’tD. can; needn’t20. ---May I borrow your bike ---No, you .A. mustn’tB. may notC. had better notD. can’tmissed the last bus, so I go home on foot.A. mustB. have toC. mayD. had tohurry if we want to arrive in time.A. mustB. needC. mayD. have to23. He get up early when he lived in the countryside.A. would B. used to C. mustn’t D. can’t24. My brother be very naughty, and my sister like reading.A. used to; wouldB. would; used toC. used to; used toD. would; would ’s clean our room,A. will youB. don’t weC. shall weD. do you26 Let us watch TV,A. will youB. don’t weC. shall weD. do youthe door after you, youA. don’tB. doC. shallD. will’s the man over thereIs it Mr Black---It be ’s much taller.not ’t not ’tvolleyball Mary’s,because her name is on it.’t be be be be!Is our headmaster giving a talk in the hall---No,it be has gone to Japan.’t not ’t ’t。