1、语法专题六：情态动词1. 常见情态动词及用法说明情态动词用法说明can1) 表示主观能力；2) 表示许可、请求；3) 表示可能性、推测，主要用于否定句、疑问句中。习语：cant help doing；cant (help) but do(不能不、只能)could 为can的过去时，具备can的各种功能，语气更委婉、客气。be able to1) 表示已能成功做到某事；2) 可用于各种时态。may1) 表示许可，允许；2) 表示可能性、推测；3) 表示祝愿（置于句首）；4) 其一般疑问句的否定回答常用: No, cant. 习语：may well (not) do很（不）可能；may as we
2、ll (not) do(不妨)might为may的过去时,具备may的各种功能,语气更委婉,可能性更小。must1) 表示主观上认为“必须”，如为一般疑问句，其否定回答常为： No, neednt / not have to. 2) 表示“偏偏、偏要”；3) 表示肯定的推测或必然。have to1) 强调客观上“不得不”；2) 可用于各种时态。should1) 表示道义上的责任； 2) 用于疑问句或感叹句中，表示意外、惊异； 3) 表示“按常理推断理应”；4) 用于 “Who should dobut”结构中，表示“除了还有谁会”。ought to与should同义，语气略重；注意其疑问式和否
3、定式。shall1) 用于第一人称，表示征求意见、请求；2) 用于第二、三人称，表示说话者的意志、允诺、命令、威胁等。3) 用在法律、条款、协定等文件中，表示义务、规定等。will1) 用于第二人称，表示征求意见、请求；2) 表示习惯；would则表示过去的习惯（只表重复动作，不表状态；used to则皆可）；3) 表示意志、决心；4) 用于if条件从句中，表示意愿。would为will的过去式，表示请求时，语气更委婉。need“需要”的意思，常用于否定句、疑问句中，无人称、时态变化，后接动词原形，否定式为neednt。dare“敢于”的意思，常用于否定句、疑问句中，无人称变化，但有时态变化，
4、其过去式为dared, 否定式为dare/dared not, 后接动词原形。习语：I dare say / I daresay: 我想，我认为2. 情态动词表示推测 1) 表示肯定的推测，用must + do / have done(过去或完成) / be doing(进行)； 2) 表示否定的推测或用于疑问句中，用can，用法同上； 3) 表示可能性的推测，用may，同法同上。 注意：以上句子的反义疑问句要根据该句的实际时态来定。巩固练习：1. Ding Junhui _ the championship; He didnt pass the first round.A. might no
5、t have won B. shouldnt have won C. couldnt have won D. mustnt have won 2. Children under 12 years of age in that country _ be under adult supervision when in a public library.A. must B. may C. can D. need3. I am sure youd rather he stayed in Spain, _? A. wouldnt you B. arent I C. didnt he D. hadnt y
6、ou4. -Could I borrow your pencil? -Of course, you _.A. can B. may C. could D. might5. You _ to the meeting this morning if you have something important to do. A. neednt to come B. dont need comeC. dont need coming D. neednt come6. I promised to get there before 5 oclock, but now the rain is pouring
7、down. They _ for me impatiently. A. may wait B. ought to wait C. could wait D. must be waiting7. Ive decided to take the job and I _ change my mind. A. mustnt B. cant C. wont D. may not8. I _ up early this morning. So I stayed in bed till 9 a. m.A. neednt have got B. didnt need to getC. shouldnt hav
8、e got D. cant have got9. The flower is dead. I _ it more water.A. will give B. would have givenC. must give D. should have given10. It is natural a man as old as he _ be very forgetful. A. can B. must C. should D. would11. The dog barked fiercely, but no one _ over to stop it.A. could go B. dare goC
9、. dared go D. might go12. We _ hurry if we want to arrive in time.A. must B. needC. may D. have to13. He _ get up early when he lived in the countryside.A. would B. will C. mustnt D. cant14. _ you please pass on a message to him?A. Do B. ShallC. May D. Will15. -Could I call you by the first name? -Y
10、es, you _.A . will B. could C. may D. might16. The fire spread through the hotel very quickly but everyone _ get out. A. had to B. would C. was able to D. could17. Its nearly seven oclock. Jack _ be here at any moment. A. must B. need C. should D. can18. -I think Helen is at home.- No, she _ be at h
11、ome, for she phoned me from the airport just five minutes ago.A. mustnt B. needntC. cant D. darent19.Hes late. What _ have happened to him?A. can B. mayC. should D. must20. After I gave her my advice, she _ go and do the opposite.A. should B. must C. shall D. ought21. Who _ come in but the president himself!A. may B. should C. can D. shall情态动词：CAAADDCBDCCAADCCCCDBB