高中英语语法——情态动词的用法（46张PPT）.ppt

1、情态动词的语法特征1)情态动词不能单独做谓语。除ought和have外,后面只能接动词原形（不带to的不定式）2)情态动词没有人称,数的变化,但有些情态动词,如can、will也有一般式和过去式的变化。3)情态动词的“时态”形式并不是时间区别的主要标志,不少情况下,情态动词的现在式形式和过去式形式都可用来表示现在时间、过去时间和将来时间。1)can的主要用法是：A.表示体力或脑力的能力：eg.The girl can dance very well.B.表示说话的推测事物的可能性等:eg.Can the news be true?C.在口语中,can可以表示请求或允许:eg.Can I sit

2、 here?can 和could：can表示“能够”时与短语be able to同义，但can只用于一般现在时或过去时，而后者可用于各种时态。另外，can表示个人有某种能力，而be able to表示某人通过努力、克服困难做成某事，相当于succeed in doing sth.如：Can you understand the different kinds of English these people are using?Two years later,he was able to speak very good Chinese.2)could的主要用法是：A.could 是can的过去式

3、,表示与过去有关的能力和推测:e.g.We all knew that the young man couldnt be a doctor.B.could可以代替can表示请求,但语气较can客气、委婉:e.g.Could you lend me your dictionary?Could I use your bike?3)can和could接动词的完成形式，表示可能已经做某事。can用在否定和疑问句中,表示不相信、怀疑等态度。e.g.They cant have gone out because the light is still on.以could或would提问时，不能再以could

4、或would作答，而应该用can或will。如：Could I borrow your dictionary?Yes,of course you can.Would you come with me?Yes,I will.may 和might：may 常用来表示：A.表示请求、允许;比can较为正式:e.g.May I come in?You may go now.B.表示说话人的猜测:“也许”“可能”:通常只用于肯定句和否定句中。e.g.-I believe the man is from England.-But I may be wrong.The guest may arrive th

5、is afternoon.在肯定句中，may的可能性比can 高，may表示现实的可能性，can表示理论上的可能性。如：The road may be blocked.这条路可能不通了。The road can be blocked.这条路可能会是不通的。在疑问句中，表示可能性用can。如：Where can he be?他会在哪呢？C.表示祝愿;但语气较正式:e.g.May you succeed!May you have a good journey!might 的用法有:多在间接引语中表示过去的可能和允许。如:She said that he might take her bike.她说

6、他可以拿她的自行车去用。除了在间接引语中以外，might 一般不表示过去的可能或者许可。如要表示过去的可能可以用could,表示过去的许可可以用was(were)allowed to 或者had permission to。表示现在的可能，其可能性要比may 小。如：She might go home tomorrow.说不定他明天会回家。表示现在的许可,语气比may较委婉,一般用于疑问句(包括间接疑问句),不可用于肯定句或者否定句。如:Might I have a word with you?我可以和你说句话吗？will和would：1.will是助动词或是情态动词？will用于构成将来时是

7、助动词。用于表示“意志”“决心”“请求”是情态动词。would亦同理。e.g.I will tell you something important.我要告诉你一些重要的事。（助动词）Will you tell her that Im here?请您告诉她说我在这儿，好吗？（情态动词）2.在疑问句中用于第二人称，提出请求或询问。e.g.:If you want help,let me know,will you?如果你需要帮助,让我知道,好吗?Will you type this,please?请打印这个,好吗？Wont you sit down?请坐下,好吗？3.would比will客气委婉

8、。e.g.:Would you help us,please?请您帮助我们，好吗？（表请求）Id go there with you.我要和你一块到那儿去。Teacher wouldnt allow it.老师不会允许这件事。（表意愿）（表许可）shall和should：1.shall用于构成将来时是助动词。shall用于征求对方的意见，表示“决心”是情态动词。e.g.:Perhaps I shall pay a visit to England this winter.可能今年冬天我会去英国观光。（构成一般将来时,助动词）Shall we go by train,Mom?妈妈，我们乘火车去好

9、吗？（用于征求对方的意见，情态动词）I shall go at once.我必须立即去。（表“决心”，情态动词）shall可以用于第一、三人称的疑问句，表示征求意见或许可；还可用于第二、三人称的陈述句中，表示允诺、警告、命令或威胁等。如：You shall be punished if you break the rule.2.should表示义务、建议、劝告，意为“应该”。“should+have+过去分词”表示本应该在过去做但没有做。eg:You should keep your promise.你应该遵守诺言。She should have passed the exam.她应该通过考试

10、的。must和 have to1.must用于一般问句中,肯定回答用must否定式用 neednt或dont have to，做“不必”,mustnt表示“禁止，不允许”Must I finish all assignments at a time?Yes,you must.No,you neednt.I dont like this TV set.We must buy a new one.There was no more bus.They had towalk home.2.表示“必须”这个意思时，must 和have to 稍有区别。must着重说明主观看法，have to 强调客观需

11、要。另外，have to 能用于更多时态。You must be the new teacher.He must be joking.There is nobody here.They must have all gone home.3.must表示对某人某事的猜测,作“准是”,“一定”,一般用于肯定句中。对过去发生的事情作肯定判断用must have done He must come and worry her with question,just when she was busy cooking the dinner.Of course，after I gave her my advi

12、ce，she must go and do the opposite.4.must表示“偏要,硬要”,指做令人不快的事情 can/could,may/might,should和must都可表示肯定的推测。can/could表示客观可能性；may表示推测时，其语气不肯定；might语气更弱，表示某事实际发生的可能性；should表示确定或可能有的未来或期待；must表示比较肯定的语气。如：I think advertisements can be quite dangerous.The newcomer may be dismissed by the company.The rescue tea

13、m should arrive by 5 oclock this afternoon.I think the old woman must be a nice person.could,might,would,should都可表示委婉语气。如:I wonder if you could let me use your cell phone.Might I know your telephone number?1.I think Ill give Bob a ring later in the week.You _.You havent been in touch with him for ag

14、es.A.will B.may C.have to D.shouldD 练习坊I.Choose the correct answer.2.John,look at the time._ you play the piano at such a late hour?A.Must B.Can C.May D.ShouldA 3.There _ any difficulty about passing the road test since you have practiced a lot in the driving school.A.mustnt be B.shant have C.should

15、nt be D.neednt haveC 4.The World Wide Web is sometimes jokingly called the World Wide Wait because it _ be very slow.A.Should B.must C.will D.can5.Helen _ go on the trip with us,but she isnt quite sure yet.A.shall B.must C.may D.canD C 6.Someone is knocking at the door._ it be Venis?No,it _ be her;s

16、he left for New York this morning.A.Can;mustnt B.Might;cant C.May;doesnt D.Can;cantD 7.Mike promised his doctor he _ not drink,and he has never drunk ever since.A.might B.should C.could D.wouldD 8.Is there a movie on in the cinema tonight?There _ be.I will phone the cinema and find it out.A.might B.

17、should C.can D.mustA 9.When I was studying at Beijing University,I _ take a walk along the lake every evening.A.willB.would C.could D.shallB10.Mr Brown,many students want to see you._ they wait here or outside?A.Shall B.Will C.Can D.WouldA can;couldWhen I was young I _ climb any tree in the forest.L

18、earning a language _ be a real challenge.couldcanII.选用正确的情态动词填空。may;mightI asked if I _ go home half an hour earlier today.There _ not be enough money to pay for the repairs.mightmay/mightwill;wouldWhen he got older,he _ never do his homework.Nancy _ keep talking unless you tell her to shut up.would

19、willshall;shouldBy now,they _ already be in Dubai.I _ be replaced by someone from the New York office.shouldshallmust;cantYou _ have stayed up.You look so tired.You _ be 45!I thought you were about 25 years old.mustcantHarvest and Thanksgiving festivals canbe very happy events.(P2)考点 情态动词can的用法。考例1

20、It is usually warm in my hometown in March,but it _ be rather cold sometimes.(福建 2008)A.must B.can C.should D.would考点点拨 考例回顾选B。can表示“可能”，意为“有时天气可能会相当冷”。must必须、肯定；should应该；would表示过去常常。考例2 You _ be hungry already you had lunch only two hours ago!(浙江2008)A.wouldnt B.cant C.mustnt D.neednt选B。此题考查情态动词表推测。cant意为“不可能”；mustnt意为“禁止、一定不要”；wouldnt常表示对现在或将来情况的虚拟；neednt意为“没有必要”。