1、 Grammar情态动词的语法特征1）情态动词 不能单独做谓语，除ought to 和have to外，后面只能接不带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。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 here?can 和could：2)could的主要用法是：A.could 是can的过去式,表示与过去有关的能
2、力和推测:eg.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:过去不可能eg.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。eg.They cant have gone out because the light is still on.may 和might：may 常用来表示：A.表示请求、允许;比c
3、an较为正式:eg.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。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：C.表示祝愿;但语气较正式:eg.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
4、might take her bike.她说他可以拿她的自行车去用。表示现在的可能，其可能性要may 小。might 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用于构成将来时是助动词。用于表示“意志”“决心”“请求”是情态动词。would亦同理。eg.I will tell you something important.我要告诉你一些重要的事。（助动词）Will you tell her th
5、at 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。eg: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。eg: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
6、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。eg: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）2.should用于第二、三人称时，表示说话者的意愿、意志，意思是“应、要、必须”。eg:I promise that sh
7、e shall get a nice present on her birthday.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 mustbuy a new one.There was no more bus.They had to walk home.2.表示“必须”这个意思时，must
8、 和have to 稍有区别。must着重说明主观看法，have to 强调客观需要。另外，have to 能用于更多时态。He must come and worry her with question,just when she was busy cooking the dinner.Of course，after I gave her my advice，she must go and do the opposite.3.must表示“偏要，硬要”，指做令人不快的事情1.-_ I go out to play,mum?-No,you_.You should do your homewor
9、k first.A.Might;wouldnt B.May;had better not C.Must;mustnt D.Need;mustntBPractice 请求许可/批准委婉地表建议2.-Where is Emma?-I cant say for sure where she is,but she_ be out shopping.A.can B.should C.must D.mayD表猜测3.How _ you say that you really understand the whole story if you have covered only part of the ar
10、ticle?A.can B.must C.need D.mayA4.There _ be any difficulty about passing the road test since you have practised a lot in the driving school.A.mustnt B.shant C.shouldnt D.needntC表预测5.Peter _ come with us tonight,but he isnt very sure.A.must B.can C.may D.willC6.-Could I call you by your first name?-
11、Yes,you_.A.will B.could C.may D.mightC7.The fire spread through the hotel very quickly but everyone _ get out.()A.had to B.would C.could D.was able toD8.-Excuse me,but I want to use your computer to type a report.-You _ have my computer if you dont take care of it.A.shant B.might not C.neednt D.shou
12、ldntA9.-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.needB10.Johnny,you _play with the knife,you _hurt yourself.A.wont;cant B.mustnt;mayC.shouldnt;must D.cant;wouldntB11.I missed the bus,so I _ go home on foot.A.must B.may C.can D.had toD
