专题4
情态动词和虚拟语气
【易错雷区，步步为赢】
(2015·北京)—Can't you stay a little longer?
—It's getting late.I really
go now.My daughter is home alone.
2.(2015·浙江)It was so noisy that we
not hear ourselves speak.
3.(2015·陕西)You
feel all the training a waste of time，but I'm a hundred percent sure later you'll
be grateful you did it.
4.(2015·四川)You
be careful with the camera.It costs!
5.—
you interrupt now? Can't you see I'm on the phone?
—Sorry Sir, but it's urgent.
6.It
be the postman at the door.It's only six o'clock.
7.(2015·重庆)Without his wartime experiences, Hemingway
(write)his famous novel A Farewell to Arms.
8.(2015·陕西)Ellen is a fantastic dancer.I wish I
(dance)as well as her.
9.(2015·天津)I wish I
(be)at my sister's wedding last Tuesday, but I was on a business trip in New York then.
10.(2015·安徽)It is lucky we booked a room, or we
(have)nowhere to stay now.
【名师点睛，易错起源】
易错起源1、情态动词的词汇义辨析
例1．(2015·天津)I
have worried before I came to the new school, for my classmates here are very friendly to me.
【变式探究】John, look at the time. __ you piano the piaho at such a late hour?
A. Must
B. Can
C. May
D. Need
【名师点睛】情态动词的基本用法
I.can(could)
1.表示体力或脑力方面的能力，或根据客观规定律能做某事的能力，意思是“能够”。can表“能够” 时，既可指将来，也可指现在。be able to 在表示能 力时与can同义，但可用:于各种时态，强调通过努力克服困难成功地做某事，相当managed to do 或succeeded in doing.例如:No one can (is able to) finish such a difficult thing.
He can speak English.
I can go there now.
With the help of the fire men , the the trapped peopel was able to leave the burning buildung(不能用could)
2.表示许可、允许，在疑问句中表示 “请求，许可”，否定句中表示 “不许”，此时可与may通采用，有时cannot可以表示 “禁止”，相当于“mustn’t”,例如:
May(Can)I help you?
That sort of thing can’t go on !
You can’t ( mustn’t, are not allowed to ) play computer games again.
3.表示推测，强调客观可能性“可能、会”，can多用于疑问句和否定句，表示猜测时，情态动词后可用进行式或完成式。
—There comes a man. Who can it be?
—It must be our English teacher.
—No, it can’t be him. He has gone to America!
He can’t have gone there alone.
4.could表示“能力”“可能性”“许可”，为can的过去式。一般用于委婉、客气地提出问题或陈述看法，此时can，could并没有时间上的差别，只是 could的语气更客气些。回答时用原形回答。
—Could I borrow your English dictionary?
—Of course you can. Go ahead.
Ⅱ.may,might( might 为 may 的过去式)
1.表示许可，有“可以”的意思，询问或说的一件事可不可以做，有时可以用can互换。其否定式 may not表示“不可以、禁止、阻止”等，常用must not =mustn’t代替，may用于疑问句中，回答这种问题时，多避免用may，而用其他形式，以免显得口气太严峻或不客气。
例如:
—Mum, may I go to the cinema tonight?
—Yes, you may.
(No, you mustn’t/ you’d better not. ) 比较:—Yes, please/please don’t.
2.表推测、或许、可能的意思，表示一件事或许会发生，只用在陈述包中。
例如:
Her
parents may come to see her tomorrow.
3.may句式用来表示祝愿。例如:
May you succeed! = I hope you may succeed.
May you be happy, healthy and wealthy!
4.might是may的过去式，表示可以做的事或可能发生的事；主句谓语动词是过去时态时用 might不用may。might一般用于比may的口气委婉，或表示现实的可能性更小一些的语境中.
例如:
Our teacher suggested a few books which I might buy.
I wonder if I might buy some sugar now.
Ⅲ.must
1.表示必须要做的事，意为“必须”，否定式 mustn’t表示“不应该，不许可，禁止”等。因此，在回答带有must的问句时，不用mustn’t，而用 needn’t或don’have to.例如:
—Must I hand in the paper now?
——Yes,you must.
—No,you needn’t./you don’t have to.
2.must在表示“必须”时与have to相近，have to比较强调客观的需要，must着重主观看法。另外 must不像have to那样能有更多的时态。例如:
Tom, you must stay at home. (命令或叮嘱)
I have to stay at home to look after my baby. (客观需要)
3.表推测，暗含很大的可能性，意为“一定”只用于“肯定句”中。例如:
I think there must be a mistake.
4.偏偏、硬要、干嘛(指做令人不快的事)。例如:
Hey, beys Must you shout so loudly?
Ⅳ.Shall
1.用于二、三人称陈述句中。表示说话人给对方的命令、许诺、警告、强制、威胁、决心等。在疑问句中，表示征询听话人是否愿意。例如:
You shall have my answer tomorrow. (允许)
He shall be sorry for it one day, I tell you. (警告)
You shall do as I tell you. (命令或分咐)
Shall you go with me? (征询意见)
2.用于一、三人称的疑问句中，表示说话人征求对方的意见和向对方请示。例如:
Shall we begin our class?
When shall my father be able to leave hospital?
V. should 和 ought to
should表示劝告、建议常作“应当”讲，与ought to有时可互换，ought to更注重一些责任义务。 should表示预测可能性，并译作“可能，(按道理)应该”；而ought to则表示非常可能。Should用于委婉、谦逊地提出意见或建议，ousht to可表示因责任、义务等该做的事。例如:
We should (ought to) help each other in work.( ought to 的语气要强)
They should come here now. (按道理应该到了)
I am your teacher, I ought to help with your study.(表示有这个责任)
Ⅵ.will和would
will可以表示意愿、意志和决心，适用于各种人称。可以用来表示各种倾向或习惯动作。有时还用来表示“难免”。其过去式是would，也可以是单独的情态动词，在表示委婉提出请求、建议或看法时，语气比will委婉，肯定的回答时用will。
例如:
Don’t worry. He will do his best.
Where there is a will, there will be a success.(表示习惯)
Accident will happen. ( 难免 )
Would you please do me a favor?
易错起源2、情态动词对话情景中的用法
例2．(2015·福建)—Sorry, Mum! I failed the job interview again.
—Oh, it's too bad.You
have made full preparations.
【变式探究】—Excuse me, but I want to use your computer to type a report.
—You __ have my computer if you don’t take care
of it.
A. can’t
B. might not
C. needn’t
D. shouldn’t
【名师点睛】
情态动词中三组表达方式的用法区别
1.would与used to的区别。
在表示过去重复的习惯时，used to可用Would代替。used to强调过去的行为同现在的对比，含有“过去怎样，而现在却不这样了”的含义；而Would则单纯表示过去的习惯动作，常与often，everyday连用，当只是表示过去的状态时，只能用used to.
例如:
They would have a drind in the bar at noon.
Thy used to have a drink in the bar at noon.(现在右能不了)
China is not what it used to be.(表示对比，不能用would)
Every evening,she would sit in frnt of the door to wait for her son .(表示过去的习惯动作，不能用used to)
They used to be a temple on the to of the mountain.(表示过去的状态，不能用would)
2.表示“宁愿做某事”时，有下列句式结构:
would rather do something
would do sth. rather than do sth.
Would rather sb. did sth.
prefer to do sth.
Prefer to do sth. Rather than do sth.
prefer to do sth. to doing sth.
【锦囊妙计，战胜自我】
情态动词否定式所表达的含义
may not,might not 或许不，可能不
can’t can not(= be not able to)不能说
can’t,can not 不可能
may not,can’t, can not, mustn’t (= be not allowed to)不许可
need’t(= don’t have to)不必
shouldn’t,oughtn’t to (= be not supposed to)不应该
易错起源3、情态动词+have
例3．(2015·重庆)You
be Carol.You haven't changed a bit after all these years.
【变式探究】—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 through
B. might go through
C. ought to have gone through
D. must have zone through
【名师点睛】
“情态动词 +过去分词”用法
1.must have done表示对过去已经发生的行为进行推测，意思是“想必、准是、一定做了某事”。
例如:
It must have rained last night, for the ground was quite muddy.
The lights were out. They must have been asleep.
2.may／might have done表示对过去已经发生行为韵推测；意思是“也许；或许、已经(没有)…”。
一般只用于肯定句或否定句中，不用于疑问句。用 might 表示语气更加不肯定。
例如:
It’s too late. I think he may have gone to bed.
He may not have finished the work. She might have caught a cold.
3.might have done表示“本来可能；…”，但实际上没有发生的事情。还可以表示“本来应该或可以做某事”的意思；有轻微的责备语气。例如:
You should not have swum in that river.
You might have been eaten by fish.
You might have given him more help, though you were busy.
4.could have done用于肯定句中，表示“可能已经……”的意义，也可以表示过去没有实现的可能性，意思为“本来可以……”。
例如:
You could have done better, but you were too careless.
I went to New York last summer and stayed at a hotel, but I could have stayed with my brother.
I saw his father just now. He couldn’t have gone to Shanghai.
5.should／ougt to have done用于肯定句时，表示本该做某事，但实际上没做；用于否定句时，则表示不该做的事反而做了。
例如:
You should/ ought to have come to the meeting earlier.
He ought not to have treated his parents like that.
6.needn’t have done表示本来不必去做的事但做了。但是didn’t need to表示”没有必要做而实际上也没有做”。
例如:
You needn’t have taken a taxi here, for it was very near to my house.
I didn’t need to clean the room.
My mother did it.
【锦囊妙计，战胜自我】
can…have done和can not have done表示对过去发生的行为的怀疑和不肯定。
例如:
He cannot have taken away the magazine.
Can he have gone home?
易错起源4、虚拟语气的一些特殊句式
例4．(2015·北京34)If I
(see)it with my own eyes, I wouldn't have believed it.
【变式探究】I would love __ to the party last night, but I had to work extra hours to finish a report.
A. to go
B. to have gone
C. going
D. having gone
【名师点睛】
虚拟语气中的几种特殊情况
1.if省略句
在条件句中，可省略if把were，had，should提到句首，变为倒装句式。如果谓语动词是否定形式时，不能用动词的缩略形式。
例如:
Should it (If it should) rain tomorrow; we would not go fishing.
Were it not (if it were not)the expense, I would go abroad now. (不能用 weren’t)
2.在would rather后的宾语从句中的虚拟语气形式用动词的过去式，在It is(hish) time (that)…句型中，从句中的谓语动词用过去式，或 should + 动词原形，但should不能省略。例如:
It is high time that you went to school.
It is high time we should start out.
I would rather they didn’t hear of the news.
3.在口语中，虚拟语气的省略情况
口语中，虚拟语气的省略情况要注意。如果是一般过去时，只保留did，could，were等助动词、情态动词或系动词如果是过去完成时，要保留had；如果是过去将来时，要保留would／might.同时还要注意被动情况。例如:
①—Have you found the answer to the question?
—I wish I had( found the answer to the question).
②I can’t go to Beijing with you, but I wish I would (go to Beijing with you).
③—Have you finished your homework?
—I would have ( finished my homework) if I had not gone to the cinema last night.
④—The liitle boy who dark the poison by mistake died if he had been sent to the hospital earlier.
—Well. he should have been (sent to the hospital earlier).
【锦囊妙计，战胜自我】
if only和 only if 句型
(1)if only可以用来表示对现在或未来的愿望,也可以表示与过去事实相反的愿望。例如: If only I could swim.(现在的愿望)
If only they would tell me what they have decided. (将来的愿望)
If only they had remembered to buy some fruit just now. (与过去事实相反的愿望)
(2)only if用于句首，后接从句主谓倒装，意思是“只要，只有”。例如:
Only if the red light comes on is there any danger to employees.
Only if a teacher has given permissionis a student allowed to enter this room