1、助动词与情态动词(一)助动词有be, have, do, will, shall。它们本身没有词义,只和实义动词的一定形式构成 复合谓语,用来表示时态和语态,构成否认、疑问及加强语气等。1、be (am, is, are, were, been)(l)“be + -ing构成进行时态;(2) be+过去分词构成被动语态;“be+动词不定式”构成复合谓语:表示按计划安排要发生的事。The prime minister is to visit Japan next year.总理将于明年访问日本。 用于命令。Youre to do your homework before you watch TV
2、.你得做完了作业才能看电视。2、have (has, had)“have+过去分词”构成完成时态。如:Have you seen the film ?“have been +-ing”构成完成进行时态。如:What have you been doing these days?这些日 子你一直在干什么?3、do (does, did)do not +动词原形”构成行为动词的否认式。如:His brother doesnt like playing basket.; (2)“Do +主语+动词原形”构成行为动词的一般疑问句。Does he go to school by bike every d
3、ay?do+动词原形”用于祈使句或陈述句中表示加强语气。jn: I did go to see him, but he wasnt in我确实去看望他了,但他不在家。Do do some work.请一定做点什么;(4)代替前面刚出现的动词以防止重复。My mother told me to go to bed early. So I did.4.will, shall (would, should)will (shall+动词原形构成一般将来时,一般来说shall用于第一人称,will用于第二人称或 第三人称,口语中常用 will 代替 shll,如:We will have a meeti
4、ng to discuss the problem.(二)情态动词情态动词没有人称和数的变化。但不能单独作谓语动词用,必须和不带to的不定式连用构 成谓语动词。只有情态动词ought要和带to的动词不定式连用,在句中作谓语用。将情态动词置于主语之前即构成其疑问式,在情态动词之后加not既构成其否认式。现将各 情态动词的基本用法分述如下:考点一情态动词的基本用法can和could的用法表示“能力。No one can be compared with Yao Ming in playing basketball.Oh, you are really his big fan.一一在打篮球方面,无人
5、能与姚明相媲美。一一你真是姚明的铁杆粉丝。表示礼貌地请求别人做某事或允许别人做某事,意为能,可以。What should I wear to the party?Well, it isnt very formal.You can wear whatever you like.一一晚会我应该穿什么?一一晚会不太正式,你可以穿自己喜欢的任何衣服。表示惊讶,常用在否认句和疑问句中。How could you do such a silly thing?你怎么能做那样的蠢事呢?1. may和might的用法(l)may和might表示许可。May I take the book out?Im afra
6、id not.我能将书带出去吗?一一恐怕不行。(2)You may come if you wish.你想来就来吧。2. must的用法表示必要性,意为“必须”。The children must be back by 4 oclock.孩子们必须4点钟以前回来。Shall I inform him of the change of the schedule right now?I am afraid you must, in case he comes late for the meeting.一一我现在通知他口程表的变动吗?一一恐怕你必须通知他,以免他开会迟到。表示禁止(用于否认句)。Yo
7、u mustnt park here! Its an emergency exit.你不可以在这儿停车!这是紧急情况出口处。3. shall 和 should 的用法shall的用法用于第一、第三人称疑问句中,表示说话人征求对方的意见或向对方请示。Shall I go out for a walk after supper?晚饭后我可以散散步吗?shall与第二、三人称连用,用于陈述句中,表示说话者的意志,用来表达说话者给对方 以命令、指示或允诺。此外,当宣布法律、规定时,也用shall来表达。如:Will you read me a story. Mummy?OK.You shall hav
8、e one if you go to bed as soon as possible.一一妈妈,给我讲个故事好吗?一一好,如果你尽快上床睡觉,我就给你讲一个。(允诺)It has been announced that candidates shall remain in their seats until all the papers have been collected.一宣布,在所有试卷收上来之前,应试者必须留在自己的座位上。(规那么或规定)(2)should的用法should意为(义务上)应该“,在语气上比must(必须)弱。“should +动词原形”表示现在或将来 应该.o如:I
9、 should go and visit him this afternoon, but I wonder if I will be free.今天下午我应该去看望他,但我不知道我是否有空。(表示将来应该)The children should be taken good care of.这些孩子应该受到好的照顾。4. will和would的用法表示意志、意愿和决心,would用于过去的情况。I have told him again and again to stop smoking, but he will not listen.我已再三告诉他戒烟,但是他就是不听。You can stay
10、 here as long as you can, if you will.如果你愿意,你能在这里待多长时间就待多长时间。(表示主语的意愿)will(wont)可用来表达真理,还可表达目前的习惯,would(wouldnt)可以用来表达过去的 习惯。如:Oil will float on water.油能浮在水面上。She will listen to records alone in her room for hours.她单独一人在屋里听唱片,常常一听就是几个小时。He would spend hours in the bathroom or on the telephone.他以前一进洗
11、澡间或是一打 ,往往就是几个小时。特别注意:would和used to都可表示过去的习惯,但前者表示过去反复的动作,常与every day, often, frequently等连用;后者表示过去的状态或过去的习惯,但现在己不存在。如: When he was abroad, he would read as many books as possible.在国外时,他总是尽可能多读 书。She doesnt get up so early as she used to.她不像以前那样起得那么早了。5. need和dare的用法need和dare两者既可用作情态动词也可用作实义动词。作实义动词时
12、,有人称和数的变化, 可用于肯定句、否认句或疑问句中,构成否认句或疑问句时要用助动词do, does, did;作 情态动词时,没有人称和数的变化,直接接动词原形,只用于否认句和疑问句中,构成否认 句和疑问句时不用助动词。另外,dare作情态动词时,还可用于条件句中,过去式为dared:作实义动词时,dare常用 于疑问句或否认句,后面的to也可省略;I dare say是习惯说法,意为“我想,大概、如: He neednt do it.(情态动词)He doesnt need to do it.(实义动词)他不必做这件事。I didnt know whether he dared say t
13、hat to him.(情态动词,有时态变化)我不知道他是否敢对他说那话。He didnt dare(to) do it.(实义动词)He dared not do it.(情态动词)他不敢那么做。考点二情态动词表示推测的用法can用于肯定句中表示客观的可能性,意为“有时会。Accidents can happen on such rainy days.这样的多雨天气可能会发生事故。(客观的可能性)can用于否认句中表推测时,语气较强。如:After what had happened he could not continue to work there.鉴于所发生的事情,他不可能继续在那里
14、工作下去了。You cant mistake their car; its got a bright red line all over it.你不可能会认错他们的车,那辆车上有道亮红色的条纹。can, could在疑问句中,常表示困惑、不相信等。如:Theres someone outsidewho can it be?外面有人一一会是谁呢?What can they be doing?他们可能在干些什么呢?Could he be serious?他当真是这个意思吗?1. may/might用于肯定句中可以用来表示不十分肯定的推测,意为“有可能;用于否认句 中也可以表示推测,may not意
15、为“可能不”,表示一种不太确定的语气。The traffic is heavy these days. I might arrive a bit late, so could you save me a place?这些天交通很繁忙,我可能会来晚一点儿。请你帮我保存个位置好吗?2. must表示推测时只能用于肯定句中,意为“一定,必定”,表示十分肯定的语气(在疑问句 中或否认句中要用can/could)eIts the office! So you must know eating is not allowed here.Oh, sorry.一一这是办公室!所以你一定知道这里不许吃东西。噢,对
16、不起。3. should用来表示推测时意为应该,即含有按道理来说应当如此”的意思。There shouldnt be any difficulty passing the road test since you have practised a lot in the driving school.因为你在驾校训练了那么多,通过路考应该没什么困难【考点三情态动词的特殊用法1. cannot but+do sth.表示“不得不/只好做某事”。如:I could not but admit that he was right and I was wrong.我不得不成认他对了,我错了。I canno
17、t choose but go.我只好去。注意:表示不得不的其它句型cant help but docant choose but docant do nothing but dohave no choice but to docannot/can never.ecough/too.表示“再 也不为过”。You cannot be careful enough to cross the road.过马路时你怎么小心都不为过。2. may可以用于祈使句,表示祝愿。如:May we never forget each other.愿我们彼此永不相忘。May you return in safety
18、.愿你平安归来。3. may well 和 may as well 结构。may well+动词原形”是一种常用结构,意为“完全能,很可能,相当于be very likely to do。如:He may well be proud of his son.他大可为他的儿子感到自豪。(2)may as well +动词原形意为最好,倒不如如:You may as well do it at once.你最好马上就做这件事。We may as well stay where we are.我们留在现在的地方倒也不错。4. “should”有时表示说话人对某事不能理解,感到意外、惊异等,意为“竟会”
19、。如:Its odd that she should think I would want to see her again.她竟然认为我会想再次见到她,真奇怪。5. must表示“偏要、硬要如:If you must go, at least wait until the storm is over.如果你偏要走,你至少要等到暴风雨停止。Must you make so much noise?你非得弄出这么大声响吗?考点四情态动词+ have done”的用法should/ought to+have done表示过去本应该做而(实际)没有做的事情,含有责备或遗憾 的语气,意为本应该其否认形式
20、为should not/ought not to+have done”,表示某种 行为本不该发生但实际上发生了。You ought to have done this exercise more carefully.你本应该更仔细地做这个练习oYou shouldnt have told her the truth.你本不该告诉她真相。1. must+havedone,用于肯定句,表示“过去一定做过某事,是一种很有把握的推测。注 意:对过去发生的情况的否认推测常用carVt/couldNt+have done”表示。Ye Shiwen won two gold medals in London
21、 Olympic Games.She must have gone through tough training.一一叶诗文在伦敦奥运会上获得了两枚金牌。一一她肯定受过严格的训练。It must have rained last night, for the road is quite muddy.昨晚一定下雨了,因为路很泥泞。2. may/might+have done是对过去情况的一种不太有把握的推测,表示“可能已做了某 事”,否认句表示“可能还没有Sorry, Im late.I might have turned off the alarm clock and gone back to
22、 sleep again.对不起,我迟到了。我可能把闹钟关掠后又睡着了。3. could + have done表示“过去本来可以做,但实际上没有做;can/could +have done表示 过去可能做过I could have saved the poor rabbit, but I didnt have the right drugs with me at that moment.我本来可以拯救那只可怜的兔子的,可是我当时没有合适的药品。4. neednl+havedone表示“过去没有必要做某事,但实际上做了某事。Mark neednt have hurried.After driving at top speed, he arrived half an hour early.马克本没必要那么匆忙。他以最快速度开车,结果早到了半个小时。You neednt have taken a taxi here, for it was very near to my house.你本来不必打车来这里的,因为这里离我家很近。
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