情态动词和虚拟语气
一、情态动词考点透析
1．can (could)，be able to。
can只有现在式can和过去式could两种形式， be able to可用于现在式、过去式、将来时、完成时。要表示“能够做某事”，可用can或be able to，但若要说过去的确运用了某种能力做成了某件事情，就只能用was/were able to，表将来具备的能力只能用will/shall be able to。
(1)If you study hard，you will be able to express freely in English in three months.
如果你努力学习，三个月后你就能自由地用英语表达了。
(2)The fire spread through the hotel very quickly but everyone was able to get out.
大火迅速在酒店蔓延，但每个人最终还是逃出去了。
2．could是can的过去式，但是在很多情况下，特别是在口语中，它表示语气的委婉。因此，用could提问时，不能用could回答，而要用can或may。would，might用于疑问句时也表委婉语气，回答时应该用will，may。
(1)－Could I borrow your dictionary?
——能借用一下你的词典吗？
－Yes，of course you can.
——可以，当然可以。
(2)－Could I call you by the first name?
——我可以直呼你的名字吗？
－Yes，you may.
——行，可以的。
(3)－Would you be so kind as to explain the word?
——请你好心地解释一下这个字好吗？
－Yes，I will.What is it?
——好的，哪个字？
3．may/might，can/could都可表示可能，但may/might 不能用于问句，can/could用于否定句、疑问句、感叹句，表示惊异、怀疑，一般不用于肯定句。如果用于肯定句，则表示偶尔发生某事的可能，或某人某物一时的特点。
(1)－Are you coming to Jeff's party?
——你会来参加杰佛的晚会吗？
－I'm not sure.I might go to the concert instead.
——说不好，我可能会去音乐会。
(2)－Where can Mr.Li be?
——李先生会在哪里呢？
－Sorry，I don't know.You can go to ask Mr.Zhang.He may help you.
——对不起，我不知道。你可以去问问张先生，他可能会帮到你。
(3)Mr.Bush is on time for everything.How can it be that he was late for the opening ceremony?
布什先生做什么都准时，开幕式时他怎么就迟到了呢？
(4)We enjoy good weather in January，but sometimes it can be terribly cold.
我们这儿一月份天气都很好，但是偶尔也会很冷的。
4．must表推测用于肯定句，其否定式要用can't。
对现在表示推测：
must do；can't do
对正在进行的动作表示推测：
must be doing；can't be doing
对过去表示推测：
must have done；can't/couldn't have done
(1)－There were already five people in the car，but they managed to take me as well.
——车里已经有五人了，但他们还是设法带上了我。
－It couldn't have been a comfortable journey.
——那就不可能是舒适的旅途了。
(2)Jack can't have arrived yet，otherwise he would have telephoned me.
杰克不可能已经到了，否则他会给我电话的。
(3)Put on more clothes，you must be feeling cold with only a shirt on.
多穿点衣服，只穿一件衬衣，你一定觉得冷吧。
(4)I didn't hear the phone.I must have been asleep.
我没有听到电话响，我一定是睡着了。
5．情态动词完成式的意义。
can/could have done
过去可能做过，过去本来可以做某事但没有做
must have done过去一定做过
may have done可能已经做过，本来可以做但没做
might have done过去可能做过，过去本来可以做但没做
can't/couldn't have done过去不可能做过某事
should (not) have done
过去本该(不该)做，但却没做(做了)
ought (not) to have done
过去本该(不该)做，但却没做(做了)
needn't have done过去本来没必要做，但却做了
would rather (not) have done宁愿过去做了(没做)
注意：must have done，may have done，might have done，can't have done都表推测。其区别在于可能性的大小。must have done表很有可能，may have done表有可能，might have done表可能性很小，can't have done则为“不可能”。
(1)I told Sally how to get here，but perhaps I should have written it out for her.
我告诉过莎莉怎么来这儿，不过也许我该写给她的。
(2)Sorry，I'm late.I might have turned off the alarm clock and gone back to sleep again.
对不起，我迟到了。我可能关掉闹钟又睡着了。
(3)I was really anxious about you.You shouldn't have left home without a word.
我真为你担心，你不该什么也不说就离家出走的。
(4)Tom needn't have got up that early since it was Sunday and he had nothing important to do.
汤姆本来没有必要起那么早的，因为是星期天，他也没什么重要事情。
(5)I would rather not have blamed him because he was a child after all.
我宁愿没有责备他。因为他毕竟只是个孩子。
6．关于should的主要用法。
(1)It's already seven o'clock.Jack should be here at any moment.
已经七点钟了，杰克随时都可能来的。
(should表推测，意为“随时都会来”，“真该来了”)
(2)－When can I come for the photos? I need them tomorrow afternoon.
——我什么时候来拿照片？我明天下午要用。
－They should be ready by 12：00.(should：应该)
——十二点前应该就可以了。
(3)You can't imagine that a well­behaved gentleman should be so rude to a lady.
你难以想象一个举止优雅的绅士对女士居然这么粗鲁。
(should表惊异，意为“居然”、“竟然”)
(4)If he should fail to come，ask Mr.Zhang to attend the ceremony instead.
要是他万一来不成，就叫张先生代替出席这个典礼吧。
(should表语气较强的假设，意为“万一”)
(5)We should have studied last night，but we went to the concert instead.(should have studied：我们本该学习的，但却没有学习)
我们昨晚本该学习的，但是我们却去了音乐会。
7．关于shall的用法。
shall用于第一人称、第三人称疑问句中，表示说话人征求对方意见或向对方请示。
shall用于第二、第三人称，表示说话人给对方的命令、警告、允诺或威胁。
(1)Shall I go on reading the text?
我要继续读课文吗？(shall：征求意见)
(2)You shall be punished one day for what you've done.
总有一天你会因你的所作所为受到惩罚的。
(shall：威胁，警告)
(3)He shall get what he deserves.I promise it.
他会得到他应该得到的，我保证。(shall：允诺)
eq \x(强化训练一)
按照句子结构的语法性和句子连贯的要求，在空白处填上适当的情态动词或根据提示使用正确形式的情态动词。
1．I ________ (not) use a clock to wake me up because at six o'clock each morning the train comes by my house.
2．I________ (not) thank you too much for all your help to my son while we were away from home.
3．—________ you interrupt now? Can't you see I'm on the phone?
—Sorry Sir, but it's urgent.
4．I got close enough to hear them speaking Chinese, and I said “Ni Hao” just as I ________do in China.
5．We ________ (not) have bought so much food now that Suzie won't be with us for dinner.
6．One of our rules is that every student________wear school uniform while at school.
7．I'm going to Europe on vacation together with John if I ________ find the money.
8．—You have to believe in yourself.No one else will, if you don't.
—I ________ (not) agree more.Confidence is really important.
9．The new law states that people ______(not) drive after drinking alcohol.
10．It's quite warm here; we ________(not) turn the heating on yet.
11．—No one ________ be compared with Yao Ming in playing basketball.
—Oh, you are really his big fan.
12．The police still haven't found the lost child, but they're doing all they ________．
13．It ________ (not) be the postman at the door.It's only six o'clock.
14．—How's your new babysitter?
—We ________ (not) ask for a better one.All our kids love her so much.
15．—I don't really like James.Why did you invite him?
—Don't worry.He ________ not come.He said he wasn't certain what his plans were.
16．If you ________ smoke, please go outside.
17．If you ______ go, at least wait until the storm is over.
18．—Shall I inform him of the change of the schedule right now?
—I am afraid you ________， in case he comes late for the meeting.
19．I ________ (not) worry about my weekend.I always have my plans ready before it comes.
20．—Will you read me a story, Mummy?
—OK.You________ have one if you go to bed as soon as possible.
答案：
1．needn't 2.can't 3.Must 4.might 5.needn't
6．shall 7.can 8.couldn't/can't 9.mustn't 10.needn't 11.can 12.can 13.can't 14.couldn't 15.might 16.must 17.must 18.must 19.needn't 20.shall
二、虚拟语气考点透析
1．虚拟语气在非真实条件句中的用法。
如：
(1)If she were here，everything would be all right.(But she isn't here now.)
如果她在这儿，一切就好办了。
(2)If you had come five minutes earlier，you would have met the famous pop singer.
如果你早来五分钟，你就可以看见那个著名的流行歌手了。
(3)If it were to rain tomorrow，the outing would be canceled.
要是明天下雨的话，郊游就要取消了。
(4)If you should visit our school tomorrow，you would see how beautiful it is.
如果你明天来参观我们学校的话，你就会发现它有多美！
2．wish＋宾语从句 (宾语从句中的动词变化如下表)。
3.在非真实条件状语从句中，如果含有were，had，should，可将if省去， 将were，had，should放在主语前，构成倒装。如：
(1)What would have happened had Bob walked farther，as far as the river bank?
要是鲍勃走得更远些，一直走到河堤上的话，会发生什么呢？
(2)Should I fail this time，I would wait for another chance.
万一我这次失败了，我会等待下次机会的。
4．在非真实条件状语从句中，有时条件从句与主句动作发生的时间是不一致的，这时动词的形式要根据动词所表示的时间来调整。这种非真实条件句叫混合虚拟条件句。如：
(1)If you had worked harder，you wouldn't be afraid of the examination now.
如果你早点努力的话，现在你就不会害怕考试了。
(2)If he had followed the doctor's advice，he would be quite all right now.
如果他早听了医生的话，他现在就好了。
5．有时假设的情况并不是以条件从句表示，而是通过一些介词短语或上下文等方式表现出来，这种句子叫含蓄虚拟条件句。or，otherwise，with，without，but for(要不是)，under 等词经常出现在含蓄虚拟条件句中。如：
(1)He hesitated for a moment before kicking the ball，otherwise he would have scored a goal.
在起脚射门时，他犹豫了一下，否则他就进球了。
(2)Without electricity human life would be quite different today.
如果没有电，人类今天的生活就会完全不同。
(3)Under more favorable conditions，the rice would grow much better.
如果条件更有利的话，水稻会长得更好。
(4)But for your help，I would still be working in the lab now.
要不是有你帮忙，我现在还在实验室埋头苦干呢。
6．情态动词的完成式大多能表示过去的虚拟事实(请参阅“情态动词”)。
7．在下列句型中动词要用虚拟语气： if it were not for要不是因为……，if it had not been for要不是因为……，if only要是……就好了！(表强烈愿望)
(1)If only he were here!
要是他在这就好了！
(2)If it had not been for the snow，we could have climbed the mountain yesterday.
要不是下雪，我们昨天就去登山了。
(3)If only he had lain quietly as the doctor instructed，he would not suffer so much now.
要是他能像医生嘱咐的那样安静地躺着的话，现在他就不会受这么多罪了。
8．would rather后的从句中，动词要用虚拟语气。如表示与现在的情形相反，动词用过去式；如表示与过去的情形相反，动词用had＋过去分词。如：
(1)Tom is com ing soon，but I would rather he came tomorrow.
汤姆很快就到了，可我宁愿他明天再来。
(2)Jane is crying sadly.I would rather you hadn't told her the bad news.
珍妮在伤心流泪呢，我宁愿你没有把那坏消息告诉她。
eq \x(强化训练二)
Ⅰ.用所给动词的适当形式填空。
1．If we ________(book)a table earlier，we wouldn't be standing here in a queue.
2.If he had spent more time practicing speaking English before，he________(be) able to speak it much better now.
3．－It rained cats and dogs this morning.I'm glad we took an umbrella.
－Yeah，we would have got wet all over if we________(not take) one.
4．Eye doctors recommend that a child's first eye exam________(be) at the age of six months old.
5．I should not have laughed if I________(think)you were serious.
6．Sorry, I am too busy now.If I ______ (have) time, I would certainly go for an outing with you.
7．We lost our way in that small village, otherwise we ________(visit) more places of interest yesterday.
8．If my car __________(be) more reliable, I would have driven to Lhasa instead of flying last summer.
9．Had they known what was coming next, they________ (have) second thoughts.
10．Jack is a great talker.It's high time that he ________(do) something instead of just talking.
11．We ________(face) the difficulty together, but why didn't you tell me?
12．Don't handle the vase as if it ________(be) made of steel.
13．We would have called a taxi yesterday if Harold ____________(not offer) us a ride home.
14．I____________(go) through that bitter period without your generous help.
15．—Where are the children? The dinner's going to be completely ruined.
—I wish they ________ (be not) always late.
16．If it________(be not) for your help，I could not have entered this famous university.
17．I would rather I________(not grow) up so that I would not worry about such a thing.
18．It is high time that we________(take)action to protect wildlife.
19．My mom suggests that we________(eat)out for a change this weekend.
20．If we________(take)the other road，we might have arrived here in time this morning for the meeting.
Ⅱ.用所给动词的适当形式填空。
Tom and Peter are twins. They look as if they 1.______ (be) the same person. Both the two boys are smart, but Tom is hard­working while Peter is lazy. Tom always wins the first place in the exams while Peter doesn't.However, people believe if Peter 2.______ (work) as hard as Tom，he would do as well as his brother in his study.
At home, their parents suggests that they 3.______(finish) their homework before playing computer games. But Peter insists that it 4.______ (be) OK to play games first as long as he can hand in his homework in time. Their mother gives in in the end.
One day, when doing his homework, Tom found he made a serious mistake. So he put his exercise book aside and used another one. When Peter found the previous exercise book, he struck out Tom's name and signed his name on its cover happily, and handed it in as his own homework the next day.
When the teacher told the truth to the twins' mother, she was very angry and shouted at Peter, “How I wish you 5.______ (be) as diligent as your brother! Now it's time that I 6.____ (give) you a good lesson. And you 7.______ play any computer games for a month！”
“Oh，no! Mom. Without a computer for such a long time, I 8.______ (die). I would rather you 9.______ (ask) me to do the dishes for a month alone.”Peter was upset.
“If you 10.________ (finish) your homework on time yesterday, you wouldn't be punished now，”said the mother.
答案：
Ⅰ.1.had booked 2.would be 3.hadn't taken
4．(should)be 5.had thought 6.had 7.would have visited 8.had been 9.might have had 10.did
11．could have faced 12.were 13.hadn't offered
14．couldn't have gone 15.were not 16.were not
17．didn't grow 18.took 19.(should) eat
20．had taken
Ⅱ.1.were 2.worked 3.(should) finish 4.is
5．were 6.gave/should give 7.mustn't 8.would die
9．asked 10.had finished
