Lesson 3 Grammarhave to / not have to, can / cant ,ought to / ought not to, ObjectivePractise using modals: Modal Verbs 情态动词情态动词 -表示必要性表示必要性have to: necessarydont have to: not necessary不必can: allowed/possiblecant: not allowed/not possible不允许/不能够ought to: advisableought not to: not advisable不应该情态动词：表示说话人的情绪、态度或语气的动词，但不能单独作谓语， 只能和其他动词原形构成谓语。第一组：表示“必须”“不得不”1. have to (1)have to表示义务、责任E.g.: You have to pass your test before you can drive.(2)dont have to(=neednt to=dont need to)表示不必E.g.: You dont have to wear uniforms at our school.P31. 三10,11 P37. 四4 (2012全国，30) I use a clock to wake me up because at six oclock each morning the train comes by my house.A. couldnt B. mustnt C. shouldnt D. neednt D.(2012天津，8) Its quite warm here; we turn the heating on yet.A. couldnt B. mustnt C. neednt D. wouldnt C.2. must(1)must表示必要性，意为“必须”,有时用于规则和法律条文的表述中。E.g: I must find a job, my parents cant support me any longer.(2)mustnt 表示禁止E.g.: Cars mustnt park in front of the entrance. 表示“ ” （是自己的一种“义务”；有时也表示一种“提议”）I must leave at six today. 我今天必须六点钟离开。I must write a letter to the head teacher. 我非得给校长写封信不可。You must go and see that filmyoud really enjoy it. 你得去看看那部电影，你会真的喜欢它的。(提建议) 必须必须must的否定式为neednt 或dont have to（不必） Must I warn him of your instruction? No, you dont have to表示就现在或将来的情况进行推测：The light is still on, so he must be at home. 灯还是亮的，他一定在家。Tell him about these and he must understand that we mean business. 他一定明白我们说的是生意。You must be hungry after a long walk. 走了很长时间路你一定饿了。注意：1. must表示推测时的否定式是 或 (不可能) ，因为must只用于肯定句，语气很强。Must our boss be at home at weekends? No, he couldnt, as he has lots of social intercourse.必定，一定cantcouldnt2. 若对过去情况的推测用must have加过去分词。The light was out. They must have gone to bed. It must have rained last night, for the ground is wet. 3. must与反疑问句中的构成就依must后的助动词a) He must be there ,isnt he? b) He must have a big family, doesnt he? c) He must be waiting outside, isnt he? d) They must have gone there last night, didnt they? e) They must have arrived by now, havent they?表示执着：If you must go, at least wait till the rain stops. 如果你坚持要走，至少也要等雨停了再走。非得，坚持(2011福建，25) -Shall I inform(通知) him of the change of the schedule(计划表,安排) right now?-I am afraid you , in case he comes late for the meeting.A. will B. must C. may D. can B.(2009全国II，20) I cant leave. She told me that I stay here until she comes back.A. can B. must C. will D. may B.(2012重庆，25) - you interrupt now? Cant you see Im on the phone?-Sorry Sir, but its urgent.A. Can B. Should C. Must D. Would C. must在疑问句中被译为“非要”(2011全国II，8) If you smoke, please go outside.A. can B. should C. must D. may C.must在条件句中被译为“非要”第二组：表示“可以”“能够”3. can(1)can表示允许或请求允许E.g.: You can go out after you have done your homework.-表示允许Can I leave?-表示请求允许表示事情可能发生E.g.: You can buy CDs at the market.表示能力E.g: I can ride a horse but I cant drive.(2)cant表示不允许/不能够E.g.: You cant go out tonight.表示事情不可能发生E.g.: You cant make bread without flour.表示在能力方面是不能的E.g.: I cant speak English.4. be able to be able to也表示能力，它与can的区别在于：be able to可以进行时态的变化E.g: I hope Ill be able to speak English well.5. couldcould是can的过去式E.g: I couldnt come yesterday.cant和mustntcant和mustnt都可以表示禁止，但从语气方面考虑，mustnt比cant更强烈，mustnt多译为“禁止”，cant多译为“不允许，不能够”E.g.: You cant/mustnt touch this switch(开关).must或mustnt多用于表示法律条文或者规章制度第三组：表示“应该”6. ought to(1)ought to表示应该做某事E.g.: You ought to visit your parents this weekend.(2)not ought to表示不应该做某事E.g.: You ought not to walk alone at night.(3)ought to表示提建议E.g.: You ought to buy a good dictionary.P31. 三7 7. should(1)should表示（义务上）应该，比must（必须）语气弱E.g.: Everyone should learn first aid.(2)shouldnt 表示不应该做E.g.: You shouldnt watch so much television.(3)should表示提建议E.g.: You should buy her flowers and apologise.may / might 的用法的用法表示推测两者都可用，只是 might 比 may 语气更不确定，表示的可能性更小。He may / might know the answer. 他可能知道答案。Do you think he may / might not be able to pay? 你认为他可能会付不起钱吗？在用法方面注意以下几点。如： 后接动词原形，表示对现在或将来的推测。如： You may might be right. 你可能是对的。 He may might tell his wife. 他也许会告诉他妻子。 后接动词进行式，表示动作正在进行或将要发生。如： He may might be writing a letter. 他可能在写信。 They may might be going abroad next month. 他们可能在下个月出国。 后接动词完成式，表示对过去可能发生的事进行推测。如： She may might have read it in the papers. 她可能在报上已读到过此事。 He may might have gone to have his hair cut. 他可能理发去了。 might 后接动词的完成式，除表示对过去的推测外，还有以下用法(不用may)。意：本来 eg. a. 表示过去某事可能发生而实际上却并没发生： A lot of men died who might have been saved很多人本来可以获救的却死了。 It was really very dangerous. I might have killed myself. 那真的是太危险了，我差点没命了。 b. 表示委婉的批评或责备。如： You might have made greater progress. 你的进步本来可更大一些的。 You might at least have answered my letter. 你至少可以回我一封信嘛。may / might as well 意：Im ready, so I might as well go now我已准备好了，因此不妨现在就走。Theres nothing to do, so I may / might as well go to bed. 既然没什么事可做，我还是去睡觉为好。This holiday isnt much fun; we might as well be back home. 这个假日过得真没意思，我们还不如呆在家里呢。 不妨、还是为好need的用法的用法 need作为情态动词只能用于否定句和疑问句，或用于由if或whether引导的宾语从句中，而不用于肯定句中。Need I type this letter again? 我需要重新录入将这封信吗？There is enough time. You neednt hurry. 有的是时间，你不必着急。The president wondered whether he need send more soldiers. 总统不知道他是否要增兵。He wondered whether they need go there. 他不知道他们是否需要去那里。 neednt have done sth. 表示 做某事,但该事却偏已经做了。You neednt have given him my name你本来没必要把我的姓名告诉他的。Weather hot, I neednt have dressed that warmly for the trip.原本没有必要 天气那么热，我本来没有必要穿那么多去旅行的。 need作为实义动词，need后面的宾语可以是名词、动名词、动词不定式或代词，这种情况下，need既可用于肯定句，也可用于否定句和疑问句，构成否定句和疑问句时要借助于助动词do或does. eg. We need a great deal of money now. 我们需要和多钱。 They dont need it any more. 他们不再需要它了。 Does your father need any help? 你爸爸需要帮助吗? need doing 与 need to be done need这种情况下应注意两点： .主动形式的动名词doing具有被动的含义； .该动名词可以改为其动词不定式的被动形式而句子的意义不变。例如： The door needs painting. = The door needs to be painted. 那扇门需要油漆一下。 Your car needs mending. = Your car needs to be repaired. 你的车需要维修了。 3need to do sth. 作为实义动词，need后面需要接带to的动词不定式,表示有义务或责任去做某事。如： What do we need to take for the picnic? 野餐我们需要带些什么？ Will we need to show our passports? 我们需要出示护照吗？ You need to take good care of your mother. 你要好好照料你妈妈 need作为名词，含义为“ ”。复数表示“基本需要”。Theres no need for you to try again. 你不必再尝试了 in (great) need of eg. The factory is in great need of funds. 那家工厂急需资金。 meet the needs of eg. This house of the 1790s can even meet the needs of the 21st century.这栋18世纪90年代的房子甚至能够满足21世纪的需要。必要；缺乏；需要急需满足的需要情态动词表示必要性时的时态变化(1)neednt have done sth.本来不必做而做了某事E.g.: You neednt have worked that late last night. It was harmful to your health.didnt have to do sth./It was not necessary to do sth.(过去)不必做某事（不强调是否做了）-就是标准的一般过去时的用法 E.g.: -Did you work very late last night?-No, I didnt. I didnt have to work very late.(2012江西，22) We have bought so much food now that Suzie wont be with us for dinner.A. may not B. neednt C. cant D. mustnt B.(2010天津，9) Mark have hurried. After driving at top speed, he arrived half an hour early.A. neednt B. wouldnt C. mustnt D. couldnt A.(2)should have done sth.=ought to have done sth.(过去)本该做而未做某事shouldnt have done sth.=ought not to have done sth.(过去)本不该做而做了某事E.g.: You should have come to the conference yesterday. What was the reason for your absence?-表示过去的必要性should do sth.表示现在或将来应该做某事E.g.: I should go and visit him this afternoon, but I wonder if I will be free.-表示将来的必要性P38. 四15(2011全国I，32) They have arrived at lunchtime but their flight was delayed(推迟).A. will B. can C. must D. should D.(2010山东，25) I have watched that movieitll give me horrible(可怕的) dreams.A. shouldnt B. neednt C. couldnt D. mustntA.注：must/could/might have done sth.表示对过去事情的推测，而不是表示必要性的含义。(1)must have done sth.想必/准是/一定做了某事(2)can/could have done sth.过去可能会做某事(3)cannot/could not have done sth. 过去不可能做某事(4)may/might have done sth.也许/或许已经做了某事