语法专题六：情态动词

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（肯定句中解释为“有时候会”。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。注意：表示“征询对方意见和允许”时，could 比can语气委婉，但回答不用could。e.g.Can/could I smoke here? Yes, you can. / No, you cant.be able to1) 表示经过一番努力之后做成某

2、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/might as well (not) do(最好，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，其肯定回答为：Yes,must.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

3、不”；2) 可用于各种时态。should1) 表示道义上的责任； 2) 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；注意其疑问式和否定式。shall1) 用于第一、三人称疑问句，表示征求意见、请求；2) 用于第二、三人称陈述句，表示说话者的意志、允诺、警告、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) 表示习惯性、倾向性；would则表示过去的习惯性、倾向性（*would只表示过去的习惯性、倾

4、向性，不涉及现在；used to 表示“过去常常”，现在已不再）；3) 表示意志、决心；4) 表示意愿。would1）为will的过去式，表示请求时，语气更委婉。2）表示过去的习惯性、倾向性。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”的意思，常用于否定句、疑问句中，无人称变化，但有时态变化，其过去式为dared, 否定式为dare/dared not, 后接动词原形。习语：I dare say 我想，我认为2. 情态动词表示推测 1)可能性由大到小顺序排列：must（肯）can（否/疑）could（肯/否/疑）may（肯

5、/否）might(肯/否) 2)对已经过去的情况推测，用“情态动词+have done”结构 must have done 肯定已经做了 cant/couldnt have done 不可能已经做了. may/might have done 可能已经做了 neednt have done 本不必做. could have done = 1 * GB3 本能够做. = 2 * GB3 可能已经做了 (在肯定句中，不可用can) should have done/ought to have done 本该做 shouldnt have done/oughtnt to have done 本不该做

6、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 not 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.

7、can D. need3. I am sure youd rather he stayed in Spain, _? A. wouldnt you B. arent I C. didnt he D. hadnt you4. -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 com

8、eC. dont need coming D. neednt come6. I promised to get there before 5 oclock, but now the rain is pouring 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 _ u

9、p early this morning. So I stayed in bed till 9 a. m.A. neednt have got B. didnt need to getC. shouldnt have 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

10、B. must C. should D. would11. The dog barked fiercely, but no one _ over to stop it.A. could go B. dare goC. 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. _

11、you please pass on a message to him?A. Do B. ShallC. May D. Will15. -Could I call you by the first name? -Yes, 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 home, 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. Af