1、四、语法详解情态动词情态动词是动词的一种，表示说话人的情感或态度。情态动词没有人称和数的变化。情态动词不能单独作谓语，必须和动词原形连用，共同构成谓语动词，有些情态动词有过去式，有些则没有。如：cancould,maymight，shall should,willwould,have tohad to,daredared,但 must,need,ought to,had better 则只有一种形式。 1.can 和 could（1）表示“现在的能力”用 can， “过去的能力”用 could。如：We can use the computer now,but we couldnt 10 ye
2、ars ago.（2）表示许可或征询对方的许可，可用 can 或 could（语气委婉，不表示过去） ，用 may较正式，注意回答时不用 could。如：Can/Could/May I come in?Yes,you can/may.（3）表示“可能性”时 can 多用于否定句和疑问句，表示 “不可能” “可能吗？” ，肯定句多用 could,may,might。如：The story could/may/might be true.It cant be true.（4）can 和 be able to 都可表示能力，但 be able to 强调经过努力，克服困难，从而能够。如：The ma
3、ths problem was very difficult,but he was able to work it out.活学巧用1.单项填空（1）(2005 浙江高考，9)The World Wide Web is sometimes jokingly called the World Wide Wait because it _ be very slow.A.should B.must C.can D.need提示：can 作为情态动词可以表示一时的情况，意为“有时候会 ”。答案：C（2）Mum,Ive been studying English since 8 0clock._I go
4、 out and play with Tom for a while?No,Im afraid not.Besides,its raining out-side now.A.Cant B.Wouldnt C.May not D.Wont提示：表示征询别人的意见。句意为：“我能不能出去和汤姆玩一会儿？”答案：A（3）_it be Li Ping who broke the glass?No.It _ be Wu Dong who did it.A.Can;must B.Must;need C.May;must D.Need;can提示：can 用于表示对疑问的推测，用 must 表示肯定的推测。
5、句意：“可能是李平打破了杯子吗？不，一定是吴东打破的。 ”答案：A2.may 和 might（1）表示“许可”或征询对方许可，否定回答时，据语气强弱为：may not,had better not,mustnt。如：You may go out with him.（现在） He told me I might stay here.（过去） May I smoke here?Yes,you may.No,you may not/had better not/mustnt.（2）表示可能性，有“或许；可能”之意，might 语气更弱。如:Im not sure whether Im coming
6、to the party.I might go to the night school instead.Lets visit him.He may be at home.活学巧用2.单项填空（1）(2005 安徽高考，26) Helen _ go on the trip with us,but she isnt quite sure yet.A.shall B.must C.may D.can提示：海伦可能会和我们一起旅行，但她还不确定。答案：C（2）Are you coming for dinner?Im not quite sure.I _go to my uncles instead.A
7、.must B.wouldC.should D.might答案：D3.will 和 would（1）will 表示意愿，用于各种人称。would 表示“过去的意愿” 。如：If you will help me,I will appreciate it.如果你愿意帮我，我会感激的。He said he would tell me the truth.他说他愿意告诉我真相。（2）will 用于第二人称的疑问句时，表示询问对方意愿或向对方提出请求。用 would 语气比 will 婉转，指现在时间。如：Will you do me a favour?Would you like to have a
8、 word with me?活学巧用3.单项填空（1）_you lend me your bike?Sure.Here is the key.A.Shall B.Must C.Will D.Does答案：C（2）_you like to have a walk with us this evening?A.Could B.Will C.Would D.Can答案：C（3）When we were young,every evening my brother and I _stay at home waiting for our mother.A.could B.might C.would D.
9、should答案：C4.shall、 should 和 ought to（1）shall 用于第一、三人称,表示征询对方的意见或主动提出干某事。第二人称用will。Shall I close the door?Shall he go out now?（2）shall 用于第二、三人称陈述句中，表示说话人的命令、警告、强制、威胁、允诺等语气。如：If you listen to me,I shall give you money.如果你听我的，我就给你钱。Tell him that he shall come to the teachers office at once.告诉他立刻到教师办公室来
10、。（3）should 表示劝告、建议，译为 “应当” ，表示主观看法。还可以表示惊奇、遗憾、必要等语气，译为“应该；竟然会” 。ought to 和 should 一样可表示劝告、建议，译作“应当” ，常表示客观情况，否定式为ought not to,疑问式为 ought sb.to You should keep your promise.你应该遵守诺言。Can you imagine that he should speak to his mother like that?你能想象他竟然那样跟他母亲说话吗？If he set out on time,he ought to be here
11、now.如果他按时出发，现在应该到这里了。（4）should 表推测，意为“ 可能”或“应该” 。This shouldnt cause any problem.这大概不会引起什么麻烦。He should be ready,I think.我想他应该准备好了。活学巧用4.单项填空（1） （经典回放）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.mightntC.neednt D.shouldnt提示：s
12、hant 表示警告，句意：“如果你不仔细使用，我不会让你用。 ”答案：A（2）When can you get my car repaired?I need it tomorrow.It _be ready by 8:00.A.must B.need C.should D.might提示：should 表示推测，译为 “应该会” 。答案：C（3）Mr.Bush is on time for everything.How _he be late for the important meeting?A.would B.shouldC.might D.need答案：B（4）I _her,but I
13、never could.A.ought to help B.must helpC.must have helped D.ought to have helped答案：D（5）Sir,you _be sitting in this waiting-room.Its for women and children only.A.oughtnt to B.cantC.wont D.neednt答案：A5.must 和 have to（1）must 表示 “必须；应该 ”，表示说话人的主观看法。 have to 作“不得不；必须”讲时，表示客观需要。must 只有一种形式，而 have to 有 has
14、 to,had to,will have to 等多种形式。如：I dont like the shoes.I must buy another pair.我不喜欢这鞋子，我应该再买一双。The pair of shoes are too small for me.I have to buy a large pair.这双鞋太小了，我得买双大的。（2）mustnt 表示“禁止；不许” 。在回答 must 问句时,否定式常用 neednt 或 dont have to。如：You mustnt play with fire.你千万别玩火。Must I hand in the homework n
15、ow?Yes,you must.No,you neednt/dont have to.（3）must “一定 ”；“肯定” ,表推测，只用于肯定句中，否定句用 cant。如：He must be a student.他一定是个学生。Mary cant be in.玛丽肯定不在家。（4）must “一定要；坚持要” ，表示主张。如：If you must go,at least wait till the storm is over.如果你坚持要走，至少也要等这场暴风雨过去了再走。（5）表示与说话人愿望相反及不耐烦， “偏要” 。如：Why must you be so stubborn?为什么
16、你偏要这么固执呢？As I was sitting down to supper,the telephone must ring.正当我坐下来用晚饭的时候，偏偏电话铃响了。活学巧用5.单项填空（1） （经典回放）Children under 12 years of age in that country _ be under adult superrision when in a public library.A.must B.may C.can D.need答案：A（2）Tom,you _leave your clothes on the floor like that!A.wouldnt
17、B.mustntC.neednt D.may not提示:句意为：“不准把衣服乱扔在地板上。 ”答案：B（3）I promised to get there before 5 oclock,but now the traffic is so heavy.They _ for me impatiently.A.may wait B.must be waitingC.could wait D.ought to wait答案：B（4）Who is the girl standing over there?Well,if you _ know,her name is Mabel.A.may B.can
18、 C.must D.shall答案：C（5）John,look at the time._you play the piano at such a late time?A.Must B.Can C.May D.Need提示：句意：约翰，看看时间，你非得这么晚弹钢琴吗？must“偏要，非得” 。答案：A6.need 和 dareneed 和 dare 作情态动词时，只用于疑问句和否定句。need 为“需要；必需” ，dare 为“敢” ，need 无过去式，dare 过去式为 dared.You neednt go there by taxi.He dare not go out alone a
19、t night.How dare you say that?注意：Need we do it now?Yes,you must.No,you neednt.活学巧用6.单项填空（1）Lucy doesnt mind leading you her dictionary.She _.Ive already borrowed one.A.cant B.mustntC.neednt D.shouldnt答案：C（2）I wonder how he _that to the teacher.A.dare to say B.dare sayingC.not dare say D.dared say答案：
20、D7.情态动词+have done（1）must have done 表示对过去发生事情的推测，意为 “想必或肯定做了某事” ，如：He was late yesterday.He must have got up late.昨天他迟到，一定是起床晚了。（2）may/might have done 对过去发生事情推测，意为 “可能、大概已做了某事” ，可能性比 must have done 小。如：John might have gone abroad,but I am still not sure about it.约翰可能已经出国了，但我还不太确定。（3）can/could have do
21、ne 用于疑问句中，表示“可能已经了吗？” 。如：The window was broken.Who could have done that?窗户被打破了，可能是谁干的呢？（4）could have done “本来可以 ”，用在肯定句中，表示本来能做却没有做。如： I could have helped you,but I had an extra task to finish.我本来可以帮助你的，但我有一个特别的任务要完成。（5）cant/couldnt have done“不可能已经做了某事” ，表示对过去情况的否定的推测。如：I didnt see her at the party.
22、She cant have been there.我在聚会上没有看见她，她不可能在那里。（6）should/ought to have done 表示“应该做而未做的责备语气 ”，shouldnt have done/oughtnt to have done 表示“不该做而做了”的后悔遗憾语气。如：You shouldnt have told him the truth.你不应该告诉他真相。（7）neednt have done 表示“原本不必做却已经做了某事” 。You neednt have come so early.你不必来得这么早。活学巧用7.单项填空（1）(2005 江苏高考，31
23、) The woman biologist stayed in Africa studying wild animals for 13 years before she returned.Oh,dear!She _ a lot of difficulties.A.may go throughB.might go throughC.ought to have gone throughD.must have gone through提示：句意为：想必她一定经历了许多困难。答案：D（2）Dont be so anxious about that.Helen _a note.A.may leave B
24、.should leaveC.might have left D.can have left提示：句意为：“海伦也许留下了便条。 ”答案：C（3）Do you still remember the day when we want to the Great Wall?I cant remember it well,but _sometime last autumn?A.might it be B.could it have beenC.could it be D.must it have been答案：B（4）You _me up.I dont have to go to work today.A.cant have wokenB.didnt wakeC.neednt to wakeD.neednt have woken答案：D
