1、情态动词基本概念情态动词作为谓语的一部分，无人称和数的变化(have to除外)；一般不能单独使用，要与谓语动词构成完整谓语，但在省略回答时，可单独使用。情态动词有can(could)，may(might)，must，have to，shall(should)，will(would)，dare(dared)，need(needed)，ought to等。观察思考Today，both male and female athletes from around the world can take part.I am sure the whole of China must have felt pr
2、oud when Xu Haifeng won the first gold medal for his country.Naturally，after I tell her what to do，my daughter must do the opposite!You should apologize to Mary for your rude remarks.Mr.Green must be a teacher，isnt he? He may come here by train，but I am not sure.Need I pay the whole amount now?There
3、 has to be a reason for his strange behaviour.归纳用法1can(could)(1)表示能力，can表示现在的能力，could主要指过去的能力。You can tell the significance of climate change to us.你可以告诉我们气候变化的重要意义。名师点津can表示能力的时候，还可以用be able to代替，can用于一般现在时，could用于一般过去时。can(could)表示具备这样的能力，但不一定做了；而be able to表示不但具备这样的能力，而且经过努力做了。Can you come to the
4、party tomorrow?明天你能来参加聚会吗？He was a good swimmer so he was able to swim to the riverbank when the boat sank.他是一个很擅长游泳的人，所以当船下沉时，他能够游到河岸上。(2)表示请求许可。当请求允许做某事时，两者均可用，但用could语气更委婉。当表示允许某人做某事时，一般要用can，而不用could。Can/Could I use your bike tomorrow morning?Yes，you can./No.Im afraid not.我明天早晨能用你的自行车吗？是的，可以。/不，
5、恐怕不行。(3)表示推测。can表推测时一般用于否定句和疑问句中(could一般无此限制)。表示对过去发生的行为怀疑或不肯定时，常用“can/couldhave过去分词”的否定或疑问形式。It cant/couldnt be true.那不可能是真的。We could go there this summer.今年夏天我们可能要去那里。(4)表示客观的可能性(并非主观推测)，意思是“有时候可能会”。The weather in Shanghai can/could be very cold in winter.上海冬季可能很冷。(5)表示惊异、怀疑，不相信的态度(主要用在否定句、疑问句或感叹句
6、中)。How can you be so careless!你怎么那么粗心呀！即学即练1选词填空：can，could，be able toMan can not live without air.Being a wise person，he finally was able to find the place.The cheater said that he could turn stone into gold.2may(might)(1)表示允许，might可以指过去时间，也可指现在时间，语气更委婉。May (Might) I ask for a photo of your baby?我可以
7、要一张你宝宝的照片吗？名师点津对may的一般疑问句的肯定回答可用may或can，但作否定回答时要用mustnt或cant。May I smoke here?No，you mustnt./Youd better not.我可以在这里吸烟吗？不，不可以。/你最好不要吸烟。(2)表示可能。可以指过去时间，也可以指现在时间，但语气不肯定。She may not know about it.她可能不知道这件事。(3)用于表祝愿的句子中。May both the bride and groom be happy!祝新娘新郎幸福！3must(have to)(1)must表示必须，没有时态变化。强调的是一种
8、主观看法，也表示责任或义务。have to表示“必须，不得不”，是由于某种外界(客观)原因而“必须，不得不”做某事，也可表示经常的或习惯性的事“必须”做。mustnt表示禁止做某事；have to的否定形式表示“不必”。have to可用于多种时态中。My brother was very ill，so I had to call the doctor at middle night.我弟弟病得很厉害，我只得半夜里把医生请来。(客观上需要做这件事)He said that he must work hard.他说他必须努力工作。(主观上要做这件事)名师点津回答must引出的疑问句时，如果是否定
9、的回答，不能用mustnt，而要用neednt或dont have to。Must we hand in our exercise books now?Yes，you must.(No，you neednt./No，you dont have to.)我们现在就必须要交练习本吗？是的，必须。(不，不必。)(2)must表示猜测。意为“想必，准是，一定”等，只用于肯定句。Shes wearing a diamond necklace.She must have a lot of money.她戴着钻石项链，一定很有钱。(3)must还可表示“偏要”。表示说话人不耐烦、不满的情绪。Why must
10、 it rain on Sunday?为什么偏要在星期天下雨？即学即练2用适当的情态动词填空My sister is ill，my mother has to look after her.Theres a lot of noise from next door.They must be having a party.Must I return all the books in three days?Yes，you must .(No，you neednt/dont have to .)If you must go，at least wait until the storm is over.4
11、shall(1)表示征询意见，用于第一、第三人称疑问句。Shall I get you some more tea?再来点茶好吗？(2)表示说话人的意愿，有“命令、允诺、警告、决心”等意思，用于第二、第三人称陈述句。You shall come on time.你必须准时到。(命令)He shall have the book when I finish reading it.我读完这本书就给他。(允诺)Nothing shall stop us from carrying out this plan.没有什么事情能阻止我们实施这项计划。(决心)(3)shall用于第三人称，表示按照法律、条文
12、或规定必须做的事，意为“应，必须”。No reader shall remove a book from the library without permission.未经许可，读者不准把书带出图书馆。即学即练3选择下列句中shall的含义A允诺B警告C威胁D征求意见You shall fail if you dont work harder.BYou shall get an answer from me tomorrow.AYou shall be punished for what youve done.CShall I watch TV for a while？D5should(1)表
13、示义务、责任。意为“应该”(某件事宜做)，用于各种人称。You should be polite to your teachers.你对老师应该有礼貌。(2)表示可能性很大的猜测，意为“想必一定，照说应该，估计”等。The film should be very good as it is starring firstclass actors.这部电影是一流演员主演的，估计拍得很好。(3)表示说话人的惊讶、愤怒、失望等特殊情感，意为“居然，竟然”。Amazing！You should wear slippers at work.真令人惊讶，你竟然穿着拖鞋上班。6will(would)(1)表示
14、意志或意愿。will指现在，would指过去，用于否定句表示“不肯，不乐意”。I will never do that again.我决不会再做那种事了。(2)表示征求意见或提出请求。主要用于第二人称疑问句中，will和would均可用，would此时不表示过去，而是表示委婉语气。Will/Would you pass me the book?请你把书递给我好吗？(3)will和would可分别表示现在和过去反复发生的动作或某种倾向，意为“总是；常常”。He will sit up there all night.他总是整夜坐在那儿。He would drop in on me on Sund
15、ays.他常常在星期天顺便过来看我。明辨异同used to，wouldused to指过去的动作或状态，着重与现在的对比，可以与过去时间状语连用would表示过去的情况，指过去的习惯动作，不说明现在的情况即学即练4用适当的情态动词填空Will/Would you please save some dessert for me?He used to be a very strong man，but now he isnt.We would sit in the yard every evening and listen to his story when we were young.7ought
16、 to(1)表示职责和义务，意为“应该”(因责任、义务等该做)，口气比should稍重。You oughtnt to smoke so much.你不应该抽这么多烟。(2)表示推测，暗含很大的可能性，近似于should。Han Mei ought to know his telephone number.韩梅应该知道他的电话号码。8need和dare(1)它们作情态动词时，后跟动词原形，常用于否定句、疑问句中。一般不用于肯定句，无第三人称单数形式。dare有过去式形式，构成疑问句时，将其移至句首；构成否定句时，直接在其后加not。Need I tell him everything?Yes，y
17、ou must./No，you neednt.我要告诉他一切吗？是的，必须。/不，没有必要。How dare she do things like that to me?她怎么敢对我做那样的事呢？(2)作实义动词时，其否定和疑问的构成需借助do/did/does，need后面接带to的不定式，而在疑问句和否定句中，dare后可省去to。有人称和数的变化。He didnt dare(to)go there.他不敢去那儿。Right now you need to stay still until help comes.现在你需要待着别动，直到有人来帮忙。即学即练5用dare/need的适当形式填
18、空You neednt hurry.There is still enough time to go.Must I go right now?No，you neednt .How dare you say Im unfair?He darent speak English before such a crowd，dare he?He needs to finish it this evening.Dont you dare touch it?9情态动词表示推测或判断的用法下表即是表示推测的情态动词使用的场合：情态动词对现在和未来的推测对过去的推测使用场合mustmustdomust haved
19、one肯定句may/mightmay/mightdomay/mighthave done肯定句、否定句can/couldcan/could docan/could have done否定句、疑问句(could可用于肯定句)should用来表示一种估计的情况“按理会/估计会”should doshould have done肯定句、否定句、疑问句情态动词have done的用法(1)should have done表示“本来应该做某事而实际上未做”，而shouldnt have done则表示“本不应该做某事而实际上做了”。You should have told me about it ear
20、lier.You shouldnt have said such words to your parents.(2)ought to have done也表示“本应该”，而ought not to have done则意为“本不应该”。You ought to have told me about it earlier.You ought not to have said such words to your parents.(3)neednt have done表示“本无必要做某事而实际上做了”。You neednt have walked so quickly since time was
21、 enough.(4)could have done表示“本来有可能而事实上未做到”。I could have come on time，but my car broke down on the way.(5)may/might have done表示“过去可能发生过某事”或“本来应该或可以做某事(实际上没做)”。You might have given him more help，but you were so busy.即学即练6补全句子I could have helped you(我本来可以帮助你的)，but I was too busy then.You must have gone
22、 to bed late(一定是睡得很晚) last night.Your eyes are red.You know the story very well.You may/might have read it(可能读过) before.单句语法填空1I have told you the truth.Must I keep repeating it?2I shouldnt have watched that movieitll give me horrible dreams.3May/Can I take the book out?Im afraid not.4You ought not
23、to watch TV now；you have a lot of homework to do.5I have taken someone elses coat by mistake.It could be Joans.I heard that she had lost her coat just now.6Is the letter from your mother?Yes.But she cant have written the letter herself，because she doesnt even know one word.7Where on earth did you ge
24、t the book?Its from Mary，if you must know.8A man is asking to meet you in the waiting room.Shall he come in?Let him in，please.9Mummy，I would really like a laptop.You shall get a laptop as long as you pass your entrance examination.10Will your mother be at home this Saturday?Hard to say.She might go
25、to the countryside to see my grandparents.短文语法填空Lucy is an outgoing lady.She 1.can play many kinds of musical instruments.Actually，she 2.could play the piano when she was 8 years old.Lucy also keeps taking exercise every day.She says that she has to do some sports because she 3.must keep slim.“You 4
26、.shall get fat soon if you dont take exercise every day.” She usually says to her friends.As for her，an elegant lady should try to keep fit.However，last week，she found that she 5.might put on weight and her husband suggested that she 6.should lose weight.However，she is always lacking in time because she has to take care of her children.One night after supper，she walked quickly to go dancing at the park.On her way，she thought that the dancing must 7.have begun(begin) and the coach 8.could have taught many new moves, but the coach was absent that night, so she was regretful.