1. 虚拟语气用于if条件句中，主从句的谓语动词形式参见上表。
If you had come earlier, you would have met him.
如果你来得早一点，你就会遇见他的。
We would go with you, if we had time.
万一有时间我们就和你一起去。
If it should rain, the crops would be saved.
如果天下雨庄稼就得救了。
2. 虚拟语气用于错综时间条件句中，主从句动作发生的时间不一致，这时主从句动词的形式应根据句意或时间来调整，选用适当的虚拟形式。
If you had listened to the doctor（过去条件 ）, you would be all right now （现在结果） .
如果当初你听医生的话，现在就全好了。
If the PLA man hadn't saved her（过去条件 ）, she would have died.（过去的结果 ）/she wouldn't be studying here now（现在结果 ）.
如果解放军当初不救她，她早就死掉了/她就不可能现在在这里学习了。
If he studied hard now（现在条件 ）, he would be a college student soon（将来结果 ）.
如果他现在努力学习，不久就会成为大学生的。
If I were you（现在条件 ），I wouldn't have missed the film last night（过去 ）.
如果我是你，昨天夜里我就不会错过那场电影了。
3. 如果条件句中包含有一个助动词、情态动词、动词be或have，有时可以把if省略掉，但这时要把助动词、情态动词、动词be或have放在主语前。
Were I in school again, I would work harder.
如果我再上一次学，就会努力学习。
Had you been here earlier, you would have seen him.
你若早一点到这里，就会见到他的。
Should there be a meeting tomorrow, I would come.
万一明天有会议，我会来的。
4. 表示 “若不是”之意时，可以用如下两种句型：
If it weren't for ... = But for ... 若不是（对现在情况的假设）
If it hadn't been for ... = But for ... 当时若不是（对过去情况的假设）
If it weren't for/But for the rain, we would be playing basketball.
若不是有雨的话，我们现在正在打篮球呢。
If it hadn't been for/But for your timely help, I would have failed in the match.
当时若不是你及时帮助，我在比赛中就失败了。
5. 在含蓄条件句中，可以用有些介词（with, without, but for）、连词（or, otherwise, but, however）、不定式短语、名词短语或陈述句表示虚拟的条件。
Without electricity , human life would be quite different today.
若没有电，今天人类的生活就会完全不同了。
A silly man would have done that.
笨蛋才会那样做。
The tree died, but I should have watered it much more.
那棵树死了，但是我真应该多浇一点水啊。
Five minutes earlier and you could have met her at the station.
再早五分钟你就可能在车站见到她了。
It would produce bad results to do that. (= If you have done that, ... . )
你若那样做的话，就有可能产生糟糕的结果。
配套练习
1. Mr. Brown _______ a house if he had enough money.
A. will buy
B. would buy
C. bought
D. has bought
2. But for John, we _______ the match last week.
A. would have lost
B. would lose
C. had lost
D. lost
3. If the child hadn't been so tired, he _______ asleep so quickly.
A. will not have fallen
B. will not fall
C. would not have fallen
D. had not fallen
4. The Smiths _______ a lovely garden if they did some work in it.
A. will have
B. would have
C. have
D. have had
5. If you learned to swim, you _______ safer in the water.
A. will feel
B. felt
C. would feel
D. feel
6. It _______ a good match if it _______
A. would have been; hadn't rained
B. will be; hadn't rained
C. would have been; shouldn't rain
D. will have been; didn't rain
7. If Mother _______ you were coming, she'd have baked some cakes.
A. has known
B. will know
C. had known
D. would know
8. Peter _______ a rich man today if he _______ more careful in the past.
A. is; had been
B. was; were
C. will be; should be
D. would be; had been
9.If I were to do this work, I _______ it in my own way.
A. would do
B. do
C. will do
D. did
10. If the plane crashed, we _______
A. would all kill
B. will all be killed
C. would all have been killed
D. would all be killed
11. _______ more carefully, she wouldn't have made so many mistakes.
A. If she listened
B. If she listens
C. If she has listened
D. Had she listened
12. If he had taken my advice, he _______ a scientist now.
A. will be
B. is
C. has been
D. would be
13. _______ , we would have visited the museum then.
A. If it does not rain
B. Should it not rain
C. Had it not rained
D. If it has not rained
14. Should it stop raining, I _______ for a walk.
A. had gone
B. went
C. would have gone
D. would go
15. _______ he try again, he might be successful.
A. Could
B. Might
C. Must
D. Should
16. If the teacher hadn't explained it to me, I _______ the problem so well.
A. would never be understood
B. had never understood
C. would never have understood
D. will never have understood
17. —Why didn't you buy that dictionary?
—I _______ if I had had enough money.
A. would
B. would have
C. have bought
D. had bought
18. If Jane hadn't missed the early train, she _______ on time, but she was late.
A. will arrive
B. would arrive
C. would have arrived
D. had arrived
19. _______ , he would be surprised.
A. Were Tom to see you
B. Were Tom see you
C. If Tom is to see you
D. If Tom has seen you
20. But for your help, I _______ the place.
A. can't find
B. can't have found
C. couldn't have found
D. haven't found
21. _______ I known he needed money so badly, I might have managed to help him.
A. Unless
B. When
C. If
D. Had
22. _______ , I wouldn't do that.
A. If I am in your place
B. Were I in your place
C. If I have been in your place
D. If I am to be in your place
23. _______ , I should paint the room white.
A. If I have been you
B. If I would be you
C. If I will be you
D. If I were you
24. If you were offered a trip to the moon, _______ you _______ it?
A. will; accept
B. are; going to accept
C. do; accept
D. would; accept
25. —Alice, why didn't you come yesterday?
—I _______ , but I had an unexpected visitor.
A. had
B. would
C. was going to
D. did
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