考点一 can,could与be able to的用法
规则1表示现在的能力用can,am/is/are able to;表示将来的能力用will be able to。
However great the difficulties may be, we can overcome them.
哪怕是再大的困难我们也能克服。
规则2表示过去的能力用could(不表示是否成功地做了);was/were able to表示过去有能力做而且成功地做了。
The fire spread through the building very quickly, but everyone was able to get out.
尽管这场大火迅速蔓延了整个大楼,但是每个人都逃了出去。
规则3 can/could表示礼貌地请求别人做某事,意为“能,可以”。
Could/Can I borrow your reference books?
我可以借你的参考书吗?
规则4 固定表达:cannot(can't)…too/over/enough表示“无论怎么……也不(过分)”,用来加强语气。cannot/couldn't but do sth不得不/只好做某事。
①You cannot be too careful. 你要特别小心。
②I couldn't but choose to wait. 我只好选择等待。
考点二 may与might的用法
规则1 表示请求、允许时,might比may的语气更委婉一些,否定回答时要用mustn't,表示“不可以”“禁止”“阻止”之意。
规则2 may/might还可以表示推测,意为“可能”。
He may be very busy these days. 他这些天可能很忙。
规则3 “may/might as well+动词原形”意为“最好,倒不如”。
If you think the price of beef is too high,you might as well buy some pork.It depends on you.
如果你认为牛肉太贵的话,你不妨买些猪肉。你自己决定。
考点三 must/have to的用法
规则1 表示“必须;应该”,must一般指主观,而have to指客观,表示“不得不”。
①We must do everything step by step.
我们必须循序渐进地做每件事。
②I have to go now for I've a meeting 15 minutes later.
我现在必须走了,因为15分钟后我有个会。
规则2 mustn't表禁止,而have to的否定式意为“不必”。
①Smoking mustn't be allowed in the office.
办公室里不许吸烟。
②—Must we hand in our exercise today?
—No, you don't have to.
“我们今天必须交作业吗?”
“不,不必今天交。”
规则3must表示推测意为“一定会”,此时不能用于否定句。
He must be ill. He looks so pale.
他一定病了,他的脸色苍白。
考点四 will, would/used to的用法
规则1 用于各种人称,表示意志或决心。will指现在,would则指过去。
I will do my best to help you in every way.
我会尽最大的努力在各方面帮助你。
规则2 用于第二人称的疑问句中表示礼貌地询问和请求,would 比 will更委婉。
Would you teach us how to drive a car?
你愿意教我们如何开车吗?
规则3 表示习惯性、经常性、倾向性,意为“总是,惯于”。 will指现在,would指过去。
He would come to see me on Sunday when he was in Beijing.
当他在北京的时候经常在星期天来看我。
规则4 表示功能,意为“能”或“行”。
He tried to open the door again, but it wouldn't open.
他再次试着开门,但就是打不开。
规则5 would 与used to
used to表示过去经常性或习惯性的动作或状态,现在已经结束,would则表示有可能再发生。
①People used to believe that the earth was flat.
过去,人们总以为地球是扁平的。(现在已不再这样认为)
②He would go to the park as soon as he was free.
过去,他一有空就去公园。(现在有可能还去)
考点五 shall/should/ought to的用法
规则1 shall表示征询意见,用于第一、第三人称疑问句。
Shall I get you some tea?我给你弄一些茶好吗?
规则2 shall表示说话人的意愿,有命令、允诺、警告、决心等意思,用于第二、第三人称。
You shall do as I say.你应该按我说的做。(命令)
规则3 shall用在条约、规章、法令等文件中,表示必然结果,多用于第二、三人称,常意为“必须”。
According to the newly-made traffic regulation,whoever drives through a red light shall be fined 200 yuan.
根据新的交通法规,不论谁驾车闯红灯,罚款200元。
规则4 should表示推测或责备,意为“想必一定,照说应该,估计”等;表推测时往往指推测有一定的依据。
The film should be very good as it is starring first-class actors.
这部电影是一流演员主演的,估计拍得很好。
规则5 should用于表示惊奇、遗憾不该发生的事情,常意为“竟然”。
Why should you be so late today?
为什么你今天竟然这么晚?
考点六 need与dare的用法
规则1 need作情态动词表示“需要,必要”。通常用于否定句、疑问句、条件句中,且只有现在时,其他时态用have to的相应形式代替。
①You needn't water the tomato plants now.
现在你不需要为番茄植株浇水。
②—Need he come now?
—Yes, he must./No, he needn't./No, he doesn't have to.
“他现在需要来吗?”
“是的,他必须来。/不,他不必来。/不,他不必来。”
规则2 dare作情态动词表示“敢于”,用于否定句、疑问句和条件句中。
①She dare not go there.她不敢去那儿。
②How dare he do such a thing?他怎么敢做这样一件事?
[温馨提示] dare和need还可以用作行为动词,其变化与一般动词相同。
①The girl didn't dare (to) go home.这个女孩不敢回家。
②Do you dare to jump into the ocean?你敢跳进海里吗?
考点七 情态动词表推测的用法
规则1can用于肯定句中表示客观的可能性,意为“有时会”;用于疑问句中可以表示推测,意为“可能”,有时表示一种惊讶的语气;用于否定句中也可以表示推测,can't意为“不可能”,语气很强烈。
You'd better put on a heavy coat.Sometimes it can be very cold here at night.
你最好穿上一件厚的大衣,在这里晚上有时很冷。
规则2may/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”;用于否定句中也可以表示推测,may not意为“可能不”,表示一种不太确定的语气。
He has a car. He may come by car, but I am not sure.
他有辆车,他可能开车来,但我不确定。
规则3 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(在疑问句中或否定句中要用can/could)。
She can't be a Danish. She must be a Norwegian.
她不可能是丹麦人。她一定是挪威人。
规则4 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 shouldn't be any difficulty about passing the road test since you have practised a lot in the driving school.
因为你在驾校练习了那么多,通过路考应该没什么困难。
考点八 “情态动词+have done”的用法
must have done 一定做过,其否定形式为can't/couldn't have done
can/could have done(虚拟)本来能够做却未做；(对过去的推测)可能做过
can't/couldn't have done(对过去的推测)不可能做过
may/might have done(对过去的推测)或许/可能做过
should/ought to have done(虚拟)本该做却未做,其否定形式表示本不该做却做了
needn't have done(虚拟)做了本没有必要做的事情
①Sorry,I'm late.I might have turned off the alarm clock and gone back to sleep again.
对不起,我迟到了。我可能把闹钟关掉后又睡着了。
②Look!There are so many mistakes in your composition.You should have fixed full attention on it.
看!你的作文里有这么多的错误。你本应该把所有的注意力都集中在它上面的。
考点九 虚拟语气
规则1if虚拟条件句的使用规则
与现在事实相反：动词的过去式(be用were)；should/would/could/might+动词原形
与过去事实相反：had+过去分词；should/would/could/might+have+过去分词
与将来事实相反：should/were to+动词原形;动词的过去式；should/would/could/might+动词原形
①If I had done it in time, I should have had a good time.
如果我及时做的话,日子就好过多了。(可惜当时没能及时做)
②If it were to rain tomorrow, I should not drive my car.
如果明天下雨的话,我就不开车了。(明天的情况还不知道)
[温馨提示] ①在条件句中,如果有were, had, should等,则可省略if,但应注意把were, had, should等提到从句主语之前。
If he were to come, I would join him in the discussion. =Were he to come, I would join him in the discussion.
如果他来,我将和他一道参加讨论。
②有些虚拟条件句没有从句,虚拟条件句是通过上下文或介词短语表示出来的。
But for air and water, there would be no life on the earth. 要是没有空气和水,地球上就没有生命。(介词短语but for提供了虚拟条件)
Without your help, we might not finish the task earlier. 要是没有你的帮助,我们可能不会提早完成任务。(介词短语without your help相当于虚拟条件句)
规则2 (should+)do…结构的虚拟语气
(1)用于表示建议、愿望、命令等动词后的宾语从句中常见的动词有:demand,order,require,insist,suggest,propose,advise,request,urge,command,prefer,desire,recommend等。宾语从句中的虚拟语气结构为“should+动词原形”,should可以省略。
The school recommends parents (should)not permit their children to swim in rivers or lakes during summer holidays.
学校建议父母在暑假不要允许他们的小孩在河里或湖里游泳。
(2)用于主语从句中
在“It is desired/suggested/proposed/recommended/necessary/important/strange/natural/a pity/essential+that从句”中,从句的谓语动词用“should+动词原形”,should可以省略。
It is suggested that the meeting (should) be put off till next week because of the bad weather.
由于坏天气,人们建议会议推迟到下周。
(3)用于表语从句和同位语从句中
在suggestion,proposal,order,plan,idea,request,advice等名词后的表语从句和同位语从句中要用虚拟语气,其构成是“should+动词原形”,should可以省略。
Your suggestion that the door (should)be shut when we leave is reasonable.
你的那个当我们离开的时候应该关上门的建议是合理的。
规则3 其他句型中的虚拟语气
(1)would rather/wish后的宾语从句中,表示愿望,意为“宁愿;但愿”。用一般过去时表示与现在或将来事实相反;用过去完成时表示与过去事实相反。
When my father is upset,he would rather we left him alone.
当我的父亲烦恼的时候,他更喜欢我们不打扰他。
(2)在“It is (about/high)time+that从句”中,谓语动词常用过去式或“should+动词原形”表示虚拟语气。
It's high time that we devoted ourselves to environmental protection and ecological improvement.
是我们致力于环境保护和生态改善的时候了。
(3)as if,as though引导的表语从句和方式状语从句中常用虚拟语气,与现在事实相反用一般过去时;与过去事实相反用过去完成时。
She speaks English as if/as though she were a native of New York.
她讲起英语来好像她是一位地道的纽约人。
(4)if only引导的感叹句中,用虚拟语气表示愿望。
Look at the trouble we're in.If only we had taken our teacher's advice!
看看我们所处的困境,要是我们接受老师的建议就好了!
误区之一 情态动词基本用法的误用
【误】 I won't thank you too much for all your help to my son while we were away from home.
【正】 I can't thank you too much for all your help to my son while we were away from home.
[分析] won't改为 can't。固定句型can't/couldn't…too…意为“再……都不为过”。
误区之二 情态动词表示“推测”语气的误用
【误】 I didn't see Mary at the meeting yesterday. She must have been ill, I guess.
【正】 I didn't see Mary at the meeting yesterday. She might have been ill, I guess.
[分析] must改为might。考查情态动词表示推测语气的运用。根据“…I guess.”可知,这是一种不太有把握的猜测,而且又是肯定句,因此must改为might。must表示推测意义时,语气较强,较肯定;can/could多用于否定或疑问句中。
误区之三 “情态动词+have done” 表示“虚拟”语气的误用
【误】 The plant is dead. Maybe I should give more water.
【正】 The plant is dead. Maybe I should have given more water.
[分析] give改为have given。根据第一句可知,植物已经死亡,所以应该是自责,故用should have done表示“本应该做……而未做”。
误区之四 条件状语从句中的虚拟语气的误用
【误】 Sorry, I am too busy now. If I have time, I would certainly go for an outing with you.
【正】 Sorry, I am too busy now. If I had time, I would certainly go for an outing with you.
[分析] have改为had。分析语境可知,从句是对现在情况的假设,故谓语的时态为一般过去时。
误区之五 宾语从句中的虚拟语气的误用
【误】 I'd rather I have a room of my own, however small it is.
【正】 I'd rather I had a room of my own, however small it is.
[分析] have 改为had。would rather后接宾语从句时,从句要用虚拟语气。根据语境可知此句是对现在情况的假设,故谓语用一般过去时。
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