1、can和could(1) 表能力（ability），“能，会” She can speak English. She could play the piano at the age of three.(2) 表请求（request）和许可（permission)，“可以”，could比can更加委婉，表示礼貌 Can I smoke here? Could I use your computer? Yes, you can.(3) can表客观可能性(possibility)，“有时候会”，用于肯定句 A wise man can sometimes make a mistake.(4) ca
2、n表推测，用于疑问句、否定句。肯定句用must Can the news be true? He cant be at home because I saw him here just now.,can/ be able to,1. be able to能用于各种时态；can/could只能表示现在或过去的能力。2.was/were able to“设法做成某事”相当于managed to do sth/ succeeded in doing sth All the people trapped in the burning house were able to get out of it.3
3、.Can的主语是人或物,be able to的主语是人 This machine can make you feel comfortable.She can/was able to sing the song in English.,may和might1. 表示允许、许可May I leave now?No, you mustnt. /Yes, you may.2. 表示推测、可能，用于肯定句和否定句，might比may可能性更小Nobody has ever seen him since that year. He may/might have gone abroad.3. May + 主语
4、 + 动词原形，表示祝愿May you succeed.,must和haveto1. must表示出于主观意识而必须要做某事；have to却表示由于某种客观原因而不得不做某事。have to自身有时态的变化形式。Must we hand in our exercises today?Yes, you must. /No, you neednt/dont have to.2. mustnt意为“不应该，禁止”3. must还可用来表示把握较大的推测，“一定”，其否定形式为can not/cant（不可能）You must be tired after your long journey.,4.
5、 must 还表示“非得, 一定 , 偏要” Must you make so much noise? After I gave her my advice，she must go and do the opposite. 5.must可表示“偏偏” 某事发生得不早不迟，就在某个当紧的时候，多指不受欢迎的事情的发生。 The car must break down just when we were starting our holidays.正当我忙碌的时候，邻居偏偏过来聊天。Just when I was busy, the neighbor must come and chat with
6、 me.,will和would1. 表示意愿、意志If you will help me with my English, I will be very happy. 2. 在疑问句中，用于第二人称，表示请求或征求意见，would比will语气更委婉Will/Would you please give me a hand?3. 表示习惯性的动作，“总是，常常” He is strange. He will sit for hours saying nothing.My mother would read me a story every night .Fish will die out of
7、water.Water will boil at 100 degrees centigrade.The door wont open.,对比would和used to1. 表示今昔动作对比，用used toI dont play tennis now, but I used to.He would get up early when he lived in the countryside.2. 表示过去的状态，用used toHe used to be a quiet boy.,shall1. shall用于第一、三人称疑问句中，表示说话人征求对方的意见和向对方请示，“好吗？要不要？”Shal
8、l I open the window for you? Shall he fetch some water for you?2. shall用于第二、三人称陈述句中，表示说话人给对方的许诺、命令、警告、威胁。You shall do as I say.Tell him that he shall have the book tomorrow.He shall be punished. Nothing shall stop me from doing it.,3. 用于条约、规定、规章等文件中，表示一种义务，多用于第三人称中。“The interest _ be divided into fi
9、ve parts, according to the agreement made by both sides.” declared the judge.A. may B. should C. must D. shall,1. Shall I / he turn on the light?2. You shall have the book after I finish it. I promise you shall see her again before long. 3. She shall not stay here any longer. You shall do as you are
10、 told. 4. That day shall come. 5. Each competitor shall wear a number.,should1. 表示劝告或建议，“应该”，相当于ought to，但语气不及ought to强You shouldnt/oughtnt to spend so much time playing computer games.2. 用于推测，意为“按理应当”.往往指具有一定的客观根据或根据推理对某事发生的“可能性”进行描述.Will Mr. Wang offer us a hand?He _ be glad to. He never refused o
11、ur request.A. can B. must C. may D. should 3. 表示吃惊，“竟会，竟然”I find it surprising that he should be so rude to you.,4. should用于表示要求，建议，命令的名词性从句中，虚拟语气 a. 用在动词insist；order, command；suggest, advise, propose；demand, desire, request, require等宾语从句中b. 用在suggestion, order, proposal, demand等后面的表语，同位语从句中。c. 用在It
12、 is/was natural (necessary/strange/ important) that；It is/was insisted (suggested/ordered) that等主语从句中,1. When can I come for the photos? I need them tomorrow afternoon. They _ be ready by 12：00.A. can B. should C. might D. need,2. Its nearly seven oclock. Jack _ be here at any moment. A. must B. nee
13、d C. should D. can,need和dare1. 作为情态动词时，两个词常用于疑问句和否定句；用作实义动词时，可用于各种句式情态动词Need I help you? Yes, please.You neednt telephone him now.How dare you talk to the teacher like that?The girl dared not go out alone at night.,实义动词We needed to tell him the news.You dont need to tell him the news.Do the flowers
14、need watering?I didnt dare (to) tell you the truth.Do you dare (to) catch the snake with your hand?The boy dares to do anything he likes.would rather do 宁愿I would rather stay here than go home.had better do 最好It is pretty cold. Youd better put on a coat.,情态动词 + have done must have done表示对过去事情的肯定推测，“
15、一定做过某事”，只用于肯定句；It must have rained last night, for the ground is wet. cant/couldnt have done表示对过去事情的否定推测，“不可能做过某事”Mr. Smith cant have gone to Beijing, for I saw him in the library just now.,can/could have done表示对过去行为的怀疑，用于疑问句，“可能做过吗？”There is nowhere to find them. Where can they have gone? I cant re
16、member when we went to Beijing but could it have been sometime last autumn? could have done表示对过去事情的假设，意思是“本来能够做某事而没有做” He could have passed the exam, but he was too careless.,may/might have done“过去可能做了某事”；may比might表示的可能性在说话人看来稍大些。may/might not have done“过去可能没有做某事”What has happened to George?I dont k
17、now. He may have got lost.He might not have finished the work.should/ought to have done“本来应该做某事，而实际没做”；shouldnt/oughtnt to have done“本来不应该做某事，而实际做了”You shouldnt have wasted time playing computer games.,neednt have done“本来不需要做某事而做了”I neednt have bought so much wine only five people came.,I was really
18、 anxious about you. You _ home without a word.A. mustnt leave B. shouldnt have leftC. neednt leave D. couldnt have left Mr. White _ at 8:30 for the meeting, but he didnt show up. A. should have arrived B. should arriveC. should have had arrived D. should be arriving Do you know where David is? I cou
19、ldnt find him anywhere.Well. He _ have gone far his coats still here. A. shouldnt B. mustnt C. cant D. wouldnt,Johnny, you _ play with the knife, you _ hurt yourself.A. wont; cantB. mustnt; mayC. shouldnt; must D. cant; shouldntThe fire spread through the hotel very quickly but everyone _ get out.A.
20、 had to B. wouldC. was able to D. couldSir, _ he go or stay? Let him go.A. will B. shall C. might D. couldTom graduated from college at a very young age.Oh, he _ have been a very smart boy then. A. could B. should C. might D. must,My sister met him at the Grand Theatre yesterday afternoon, so he _ y
21、our lecture.A. couldnt have attendedB. neednt have attendedC. mustnt have attendedD. shouldnt have attendedIt has been announced that candidates _ remain in their seats until all the papers have been collected.A. can B. willC. may D. shallThere was a lot of fun at yesterdays party. You _ come, but w
22、hy didnt you?A. must haveB. shouldC. need haveD. ought to have,This cake is very sweet. You _ a lot of sugar in it. A. should put B. could have put C. might put D. must have putI _ have been more than six years old when the accident happened.A. shouldnt B. couldnt C. mustnt D. needntThe woman biologist stayed in Africa studying wild animals for 13 years before she returned.Oh, dear! She _ a lot of difficulties! A. may go through B. might go throughC. ought to have gone through D. must have gone through,
