英语语法网
英语语法学习中，对于虚拟语气的应用也是比较常见的。下面是学习啦小编给大家整理的英语语法网的相关知识，供大家参阅!
英语语法网：虚拟语气用在其它名词性从句中
1.虚拟语气用在 suggest, demand, insist, ask, move, advise. desire, order, propose, require, recommend, request, maintain, vote 等表示建议，命令，请求的动词后的宾语从句中，从句的谓语用 should + 原形动词，但美国英语中常要省去 should 。例如：
I suggest we start at once.
They propose that you (should) read the rules carefully.
The commander ordered that the soldier fire at the enemy.
He insisted that he go there on foot.
I move that the meeting be adjourned. 我提议休会. move:(在会议上)提议，动议
Example:
He insisted that we all ______ in his office at one o'clock.
a. be b. to be c. would be d. shall be
He asked that it ______ done right away.
a. is b. be c. shall be d. must be
He recommended that John ______ with him.
a. must go b. went c. will go d. go
2.虚拟语气用在 It is + 形容词(或过去分词)+ that... .的主语从句中，表示要求，建议，提议，命令，请求等，英国英语中从句的谓语用“should +原形动词(或完成式)构成”，而美国英语中则要求用原形动词。该句型中常用的形容词或过去分词有：advisable, desirable, essential, important, better, keen, natural, necessary, probable, possible, strange, vital, desired, demanded, requested, suggested, recommended, required 等。例如：
It is necessary that the machine (should) be oiled once a week.
It is important that everyone (should) obey the law.
It is suggested that you take a walk after supper.
Example:
It is necessary that he ______ in time to attend the meeting.
a. come b. came c. would come d. need come
It was proposed that the matter ______ discussed at the next meeting.
a. would be c. will be c. was d. be
It is strange that she ______ in the last examination.
a. should have failed b. have failed c. would fail d. failed
3.虚拟语气用在与表示建议，要求，提议，命令，请求等意思有关的同位语从句和表语从句中，英国英语中要求从句谓语用“ should + 原形动词”，而美国英语中则要求用原形动词， 但在 as if, as though引导的表语从句中，从句中谓语用动词过去式或过去完成式，表示对现在或过去的虚拟。例如：
He complied with the requirement that the experiment (should) be done tomorrow.
他同意明天再做实验的要求。虚拟语气用在其它名词性从句中
He looks as if he were tired.他面带倦容。
We agree to the suggestion that they (should) work on night shifts in turn.
我们同意轮流值夜班的建议。
His order is that you (should) send the materials to the work site at once.
他的命令是你们要把材料立即送到工地。
Example:
Your advice that she ______ till next week is reasonable.
a. will wait b. is going to wait c. waits d. wait
Jane appears as though she ______ the secret.
a. knows b. has known c. had known d. knew
He looked as if he______ ill for a long time.
a. was b. were c. has been d. had been
4.虚拟语气用在 It is (high, about) time (that) 句型中，定语从句中谓语用动词过去式，意指将来。例如：
It is time (that) we went home.
It is high time we had the meeting.
It is time you left.
It is time that I was off.
注：如果主语是单数第一，三人称，动词 be常用 was 。
Example:
We've been sitting here doing nothing about it for days. It's time we ______ the problem.
a. shook hands with b. got to brass tacks with
c. got to grips with d. reached the bottom of
词组 get (or come) to grips with 为“开始努力对付”。
It is high time we _______ off.
a. are b. were c. be d. will be
It is ______ we did something about redecorating the sitting room.
a. high time b. long time
c. good time d. full-time
练习题：
1. The doctor suggested that he ______ a short leave of absence.
a. will take b. would take c. take d. took
2. We demand that atomic weapons ____ .
a. be prohibited b. will be prohibited
c. are prohibited d. ought to be prohibited
3. It was suggested that transistors _____ in such devices.
a. should be used b. should use
c. can be used d. were using
4. The tutor recommended that she _______ this book.
a. must buy b. buy
c. should have bought d. buys
5. The housemaster was strict. He requested that we ______ television on week nights.
a. not watch b. must not to watch
c. not be watching d. have not watched
6. My father did not go to New York, the doctor suggested that he ______ there.
a. not to go b. won't be
c. not go d. not go to
7.I demanded that the students each ______ a plan for the summer vacation.
a. would make b. will make c. make d. made
8. It is surprising enough that such a horrible thing ____ there.
a. happened b. will happen
c. should happen d. has happened
9. It was urgent that she ______ the master immediately.
a. call b. calls c. called d. would call
10. He looks as if he _____ nothing about it before.
a. knows b. had known
c. has known d. wouldn't know
11.My idea is that we ______ the challenge.
a. ought accept b. will accept
c. accept d. are accepted
12. The sun rises in the east and sets in the west, so it seems as if the sun ______ round the earth.
a. is circling b. has circled
c. should circle d. were circling
13. It was suggested at the meeting that effective measures _______ to solve the problem.
a. be taken b. must be taken
c. were taken d. take
14. It's advisable that he ______ with a clearly defined goal in mind.
a. must go b. go c. will go d. goes
15.It seemed as if all of sudden the animal _____ danger in the air.
a. has smelt b. had smelt
c. smelt d. would smell
16.It is better that the book ______ on the low stool.
a. put b. puts
c. should be put d. be put
17.He moved that the report ______.
a. should accept b. should be accepted
c. be accept d. would be accepted
18.The professor gave orders that the test ______ before 5:30.
a. be finished b. will be finished
c. will finish d. shall finish
19.It's time he ______ something for his coming examination.
a. do b. does c. will do d. did
20.It was essential that all the necessary documents ______ to the dean's office before Friday.
a. be handed in b. must be handed in
c. had been handed in d. should hand in
21.It is highly desirable that a new president _____ for our institute.
a. appointed b. be appointed
c. has been appointed d. is appointed
22. The government ordered that the pollution problem of this city ______ within six months.
a. would solve b. would be solved
c. should be solved d. must solve
23. It is natural that much research ______ to overcome corrosion.
a. should make b. will make
c. is made d. should have been made
24. It is important that a consultant engineer ______ familiar with modern developments.
a. is b. being c. be d. has been
25. Since her blood pressure is much higher than it should be, her doctor insists that she _____.
a. will not smoke b. is not smoking
c. didn't smoke d. not smoke
英语语法网：虚拟语气用在条件状语从句中
虚拟语气是一种特殊的动词形式，表示所说的话不是一个事实，而只是一种假设，愿望，建议，怀疑，猜测或不大可能实现的空想。
I.虚拟语气用在条件状语从句中
虚拟语气用在条件状语从句中，通常从句由连词if 引导。
1.与现在事实相反的虚拟条件句
条件状语从句主句
If +主语 +动词过去式主语+ would, should, could, might+原形动词
(be的过去式用were)
例如：
If I feared death, I wouldn't be a communist.
(刘胡兰)怕死就不做共产党员。
If there were no air, we couldn't live.
如果没有空气，我们就不能生活。
Example:
I would ask George to lend us the money if I ______ him.
A. had known B. knew C. have known D. know
I _____ it to him if I thought he would understand.
A. shall explain B. will explain C. would explain D. explain
2.与过去事实相反的虚拟条件句
构成
条件状语从句主句
If + 主语 + 动词过去完成式主语 + would, should, could, might+have + 过去分词
例如：
If you had come a few minutes earlier, you would have met him.
如果你早来几分钟，你就会碰上他。
If there had been no air in the tube, the result of the experiment would have been more accurate.
如果试管中没有空气，实验结果就会更精确。
Example:
If you hadn't gone with Tom to the party last night, _______.
A. you would meet John already
B. you won't have missed John
C. you will have met John
D. you would have met John
3.与将来事实相反的虚拟条件句
构成
条件状语从句主句
If + 主语+ should +原形动词主语+would,should,could,might或were+不定式+原形动词
例如：
If he were to come tomorrow, things would be easier.
假如他明天会来，事情就容易办了。
If the sand should be broken up, it would give out much energy.
如果沙子能被分解，它会释放出大量的能量。
注：在表示与将来事实相反的虚拟条件句中，从句中的should有时可以省略。如：
If he make the design, he might do it in some other way.
要是他来搞这个设计，他可能用另外的方法设计。
Example:
If the sea ____ to rise 50 feet, India would become an island.
A. will B. is C. was D. were
If you ____ to see Mary, what would you tell her?
A. are B. will be going C. must D. were
We might still catch the train if we ___.
A. make hurry B. haste
C. make haste D. hastily
4.错综时间的虚拟语气
在一些含有虚拟语气的句子中，如果主句与从句的谓语表示不同的时间，虚拟语气可有不同形式，即主句与从句各自按自己的时间构成虚拟形式。例如：
If I had met him before, I could recognize him.要是我以前遇见过他，我就能认出他了。
(从句表示与过去事实相反，主句表示与现在或将来事实相反)
If we were driving at a speed of 100 Li an hour, we would have arrived there 2 hours ago. 如果我们的行车速度每小时100里，两小时以前我们就会到达那里了。
(从句与现在事实相反，主句与过去事实相反)
Example:
If you _____ that late movie last night, you wouldn't be sleepy.
A. haven't watched
B. didn't watch
C. hadn't watched
D. wouldn't have watched
5.省略连词if
在条件状语从句中，如果有were, should, had，可以把连词if 省去，把 were, should, had 放在句首，构成条件意义。例如：
Should it rain tomorrow, what would you do? 万一明天下雨，你怎么办?
Were there no friction, we could not walk. 要是没有摩擦力，我们就不能行走。
Had we known about the new method, we should have applied it earlier.
如果我们过去知道这种新方法，我们早就应用了。
Example:
Had Alice been more hardworking, she _______.
A. had not failed B. would not fail
C. could not be failed D. would not have failed
_______ today, he would get there by Friday.
A. Would he leave B. Was he leaving
C. Were he to leave D. If he leaves
______ difficulties, we would be successful.
A. Should we overcome B. Would we overcome
C. Might we overcome D. Could we overcome
6.虚拟结构中省略主句或从句
虚拟结构中有时可省去主句或从句，并不影响意义的完整。
(1)省去条件从句
That would be fine. 那太好了。(省去了if you would come 或类似条件)
I wouldn't pass up the chance to visit China. 我不会放弃访问中国的机会。
We might have produced more coal. 我们可能生产出更多煤炭。
注：省略条件句，在试题中很少见到。
(2)省去主句，常用以表示愿望。从句谓语多用过去时或过去完成时。
If only she were here. 假如她在这儿该多好啊!
If only he lived! 假如他活着该多好啊!
If only I had known it before. 如果我早先知道这件事，那就好了。
Example:
If only it _____! but it is too late.
A. is avoided B. has avoided
C. could be avoided D. can be avoided
If only everything _____ out as we wanted it to in life!
A. is working B. worked
C. works D. has worked
英语语法网：虚拟语气用在其它状语从句中
1.虚拟语气用在由as if, as though 引导的方式或让步状语从句中，一般情况下，如果主谓语动词为现在时，从句谓语多用过去时;如果主句谓语为过去时，从句谓语多用过去完成时。虚拟语气用在 even if, even though, whatever引导的状语从句中，从句谓语可参照由if引导的虚拟条件从句的谓语，一般用过去时或过去完成时。例如：
This old machine runs as if it were a new one.
The old worker works as though he were a young man.
Even though she had been here very soon, she would not catch the train.
Example:
He has just arrived, but he talks as if he ______ all about that.
a. know b. knows c. known d. knew
I can't stand him. He always talks as though he _____ everything.
a. knew b. knows c. has known d. had known
______ I used a lot of examples I still could not get my idea across.
a. Since b. But that c. Now that d. Even though
2.虚拟语气用在so that, lest (唯恐), in case (万一), unless, in order that(为了，以便), that(为了，以至于), for fear that (生怕，以免), on condition that (如果)等引导的目的，条件状语从句中，从句谓语 may 或 might+原形动词，也有用 should, can, could+原形动词构成的。例如：
The teacher explained the law once more in order that we might understand it better.
Some people eat so that they may live. Others seem to live in order that they may eat.
一些人吃是为了生存，而另一些人似乎是活着就是为了吃。虚拟语气用在其它状语从句中
I left him a note with my address on for fear that he should not know where to see me.
The heroes gave their lives that we might live a happy life.
为了我们过上幸福生活，英雄们献出了自己的生命。
Example:
In case I ______, I would try again.
a. will fail b. would miss c. should fail d. shall miss
You should exercise vigilance _____ you should be killed.
a. so that b. lest c. therefore d. that
3.虚拟语气用在由 “whether” 引导的让步状语从句中，从句谓语用原形动词。例如：
All engines work on this principle, whether they be large or small.
所有发动机都按这一原理工作，无论它们是大还是小。
We must finish the work before we go home, whether it be early or late.
无论时间早晚，我们必须在回家前干完工作。
All matter, whether it be gas, liquid or solid, is made up of atoms.
所有物质，不论是气体，液体，或固体，都是由原子构成。
在此句型中，可省去 whether ，而将be放在主语前。例如：
Be it so, we must continue to do the test.
We must do our best to fulfil the task, be it ever so hard.
Example:
______ I'll marry him all the same.
a. Were he rich or poor b. Be he rich or poor
c. Whether rich or poor d. Being rich or poor
练习题：
1.______, I must do another experiment.
a. It is ever so late
b. Ever so late it
c. Be it ever so late
d. Whether be it ever so late
2.The young driver looked over the engine carefully lest it ______ on the way.
a. goes wrong b. would go wrong
c. went wrong d. should go wrong
3.Machines are often oiled so that they ______ well.
a. ran b. runs c. should run d. running
4.Even if he ______ very busy, he would have kept on learning English.
a. had been b. was c. were d. had being
5.Supposing the weather ______ bad, where would you go?
a. is b. will be c. was d. were
6. ______, he could not succeed.
a. However, he tried that
b. He tried however hard
c. However he could try
d. However hard he tried
7. Even though the enemy ______ wings, they couldn't escape from our encirclement.
a. had b. had had c. have d. has
8.She described the accident as if she ______ it herself.
a. saw b. has seen c. had seen d. sees
9.He came to meet us at the station for fear that we ______ the wrong way.
a. take b. should take c. took d. had taken
10.The car looked very dirty, as though it ______ hundreds of miles.
a. run b. runs c. has run d. had run
11.The teacher spoke slowly in order that we ______ no difficulty in following him.
a. should have b. had
c. will have d. didn't have
12.All magnets behave the same, ______ they large or small.
a. how b. are c. be d. were
13.At the beginning he didn't want to speak English lest he _____ mistakes.
a. will make b. should make
c. would make d. can
14. I remember the whole thing as if it ______ yesterday.
a. happen b. happens c. happened d. happening
15.She stayed at home for a few days so that she _____ her mother.
a. takes care of b. took care of
c. might took care of d. might take care of
16.She took up the meter with care for fear that it _____ .
a. is damaged b. to be damaged
c. should be damaged d. was damaged
17. In many cases the heating effect is neglected as if there ______ no flow of current along the wire.
a. are b. were c. is d. being
18.I'll put the money on the table just in case you ______ it.
a. might need b. would need
c. needed d. may have needed
19.Providing you ______ the opportunity to go abroad, which country would you want to visit first?
a. have b. will have c. had d. have had
20.The business of each day, ______ selling goods or shipping them, went quite smoothly.
a. it being b. was it c. it was d. be it
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