一、        以suggest. insist. demand为代表的一类表示建议、命令、要求、想法等动词后跟从句（一般为名词性从句）时。从句部分需要用虚拟。其表现形式体现在从句的谓语动词用should加动词原形或动词原形。

二、在if引导的非真实条件状语从句中，需要根据时态语态的不同使用虚拟。可分为以下三种：

1.      对过去的时态进行虚拟

If he had worked hard, he would have got through the exam.

条件句用 过去完成时态

主句用would/ could/ might + have done

2.      对现在的时态进行虚拟

If I were twenty, I would be studying in a college now.

I get a high salary , and I am satisfied with my job.

If I got a high salary, I would be satisfied with my job.

条件句用 一般过去时态

主句用 would /could/ might + 表示现在的时态

3.      对将来的时态进行虚拟

If he were to set out tomorrow, he would hold a farewell party tonight.

条件句用 were to + 动词原形

主句用 would /could / might +动词原形

 

一般情况下，以完整的非真实条件句(即有主句和从句)形式表现出来的虚拟语气，我们可以将其从句看作真实条件句情况下的时态向前推；其主句则为would/ could/ might +句子所需要的时态。

三、在would rather, would sooner, had rather, would just soon等表示“宁愿”“最好”的意思，后面加从句时需要用虚拟。其表现形式体现在从句的谓语动词需要用一般过去式或者过去完成式。

I’d rather have the small one that the big one.

I’d rather stay than go out.

I would rather you had not done anything about it at that time.

Wouldn’t you rather he cooperated with you ?

四、在wish, if only, as if, as though 引导的表示与事实相反或不能实现的从句中，从句用虚拟，根据时态不同表现为三种形式：(请注意与第二种的比较)

1.      对现在的虚拟----用过去时态表现

Tom always has the wish that he lived in a big city like New York.

My uncle wishes he were a young boy.

He talks as if he had been abroad. (现在完成---过去完成)

2.      对过去的虚拟-----用过去完成时态或者would; could, might加现在完成时态

I wish that she had been / would have been here tomorrow.

If only he had taken / would have taken my suggestion.

3.      对将来的虚拟------表现为would; could, might加动词原形

If only my father would not ask my score after the exam.

She weeps as though her heart would break.

五、在It is (was) + adj + (that) clause的形式主语结构中，从句通常要用虚拟。表现为should加动词原形或者直接用动词原形。(注意与第一种虚拟的相似之处)

It was essential that these blank forms be filled.

六、It is time后面加从句时常用虚拟，表现为从句谓语动词用过去式或者过去完成时。

七、以lest; in case; for fear that 等引导的状语从句中用虚拟，表现为从句谓语动词用过去式或者should+动词原形。

He takes an umbrella in case it rains (现在表示将来,没有虚拟)/ it should rain/ it rain.(虚拟)

 

本节中涉及到的情态动词很多，特别注意下列几种形式的区别：

could/ would/ might + have done 用于对过去虚拟中

should / ought to + have done 表示本该做但是没有做

must + have done 表示对过去的肯定猜测

can’t + have done 表示对过去的否定猜测

need + have done 本来需要做 (注意否定时与shouldn’t have done 的区别)

 

练习:

1. He left orders that nothing _________ until the police arrived.

A.     was touched 　　       B. had been touched

C.     should be touched 　　      D. were touched

2. If only I ___________ differently, he might still be alive now.

A.     had behaved     B. behaved　  C. have behaved   D. behave

3. I wish I __________ to the movie with you last night.

A.     went      B. could go　    C. go 　  D. could have gone

4. Without his permission, there ______ no such opportunity offered.

A.     would be 　　  B. was　　       C. will be 　　  D. are

5. But that he saw it, he ______________ it.

A.     couldn't have believed 　　     B. didn't believe

C.     could not believe    　　             D. can't believe

6. Jean Wagner's most enduring contribution to the study of Afro-American poetry is his insistence that it _________ in a religious, as well as worldly, frame of reference.

A.     is to be analyzed 　　        B. has been analyzed

C.     be analyzed   　　     D. should have been analyzed

7. _________ no friction between the surface of the road and our feet, we could not walk at all.

A. If there was 　　 B. Were there　   C. Was there 　 D. There had

8. Suppose the knife _________ accidentally, would the doctor get his fee from the person he is treating?

A. slipped 　　  B. is slipping　　  C. had slipped　　  D. would slip

9. The article suggests that when a person __________ under unusual stress he _________ especially careful to have a well balanced diet.

A.     were, be 　  B. is, should be　  C. was, will be 　  D. be, be

10. Had Paul received 6 more votes in the last election, he _______ our chairman now.

A.     must have been      B. would have been　  C. were   D. would be

11. He suggested ______ to tomorrow's exhibition together.

A.     us to go 　　         B. we went 　　 C. we shall go 　  D. we go

12. _____ today, would we be able to get there by Tuesday?

A.     Were we leaving 　　                 B. If we leave

C.     Would we leave 　　                 D. Were we to leave

13. If he ______ drunk, he wouldn't have lost control of the car.

A.     wasn't 　　 B. weren't　  C. hasn't been 　  D. hadn't been

14. I would have gone to the concert, if I _____ time.

A.     had had 　　 B. have had 　　 C. had 　    D. would have had

15. _______ I known it, I would have told you.

A.     Have 　　  B. If 　　    C. Had 　　    D. Having

16. ______ your help, I would not have succeeded.

A.     Because 　　 B. Because of 　  C. But 　   D. But for

17. The house master 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

18. How I wish that the disabled _____ good care of.

A. will be taken  B. would be taken  C. must be taken  D. be taken

19. If Sydney Carton _____ Charles Darney , the latter _____.

A. didn't help; would die          B. hadn't helped ; might die

C. hadn't helped ; would have died   D. shouldn't help; should have died

20. He has never traveled in any big cities, but he talks about London as if he _____ there.

A. has been       B. has gone  C. had been     D. had gone

21. Holmes made a demand that he as well as his assistant ______ in the lady's room that night.

A.     should lock   B. be locked     C. would be locked   D. was locked

22. You have failed again. I think you _____ harder.

A.     ought have studied          B. ought to have studied   

C.     must have studied           D. may have studied

23. You ___ in such a hurry. After all, the station was quite near the hotel.

A.     must have been             B. should have been

B.     needn't have been          D. might have been

24. Had you taken the doctor's advice, you ______ all right now.

A.     are      B. were       C. would have been        D. might be

25. I don't think it is the right time that you ______.

A. will go      B. went       C. go         D. must go

26. It is necessary that you ______ spoken English now and then.

A. might practise  B. practised  C. should practise  D. would practise

27.His room looks very dirty as though it _______ for years.

A. has not been cleaned           B. were never cleaned  

C. had not been cleaned           D. was not cleaned

28. On the boy's face, there was a sweet smile, which suggested that he _____ happy to give his life for his country.

A. should be    B. was      C. had been       D. would be

29. You _______ earlier. The bus left a moment ago.

A.     would have come                     B. should have come   

C.     might have come                     D. must have come

30. ______ that the old man give up smoking.

A.     It is requested                  B. It is hoped    

C. It is wished                         D. It is reported