虚拟语气在条件状语从句中的应用
【经典例题】
1. If my lawyer _______ here last Saturday, he _______ me from going.
A. had been; would have prevented B. had been; would prevent
C. were; would prevent D. were; would have prevented
2. If I had worn my overcoat, I _______cold.
A. won’t have caught B .couldn’t have caught
C. won’t catch D. wouldn’t catch
3.—If he ______ , he ______ that food.
—Luckily he was sent to the hospital immediately.
A. was warned; would not take B. had been warned; would not have taken
C. would be warned; had not taken D. would have been warned; had not taken
4. I didn’t see your sister at the meeting. If she _______, she would have met my brother.
A. has come B. did come C. came D. had come
【答案与解析】
1．A．本题考查虚拟语气。因为从句表示与过去事实相反的假设，故从句谓语动词用过去完成时，而主句谓语动词用would have +过去分词形式。
2．B．本题考查虚拟条件句中主句谓语动词的使用。因为从句用了过去完成时，可知主句谓语动词用would / could have +过去分词形式。根据句意，可知选B。
3．B. 根据答语，可知本题考查与过去事实相反的虚拟语气。故从句谓语动词用过去完成时，而主句谓语动词用would have +过去分词形式。
4．D． 根据句意“在会上我没有看到你的姐姐。如果她来的话，她就见到我哥哥了”可知，这是考查对过去事实的虚拟。主句用could have done，故从句谓语动词应该用过去完成时。
【重点归纳】
一、虚拟条件句的类别
虚拟条件句可分为三类：一类是叙述与现在事实相反的情况；一类是叙述与过去事实相反的情况；另一类是叙述与将来事实相反的情况。其主句和从句的谓语动词构成如下：
1. 与现在事实相反
条件从句用过去时（be动词的过去式一律用were），主句用would （should/ might / could）+动词原形”。如：
If I were you, I would accept the invitation to the party.
如果我是你的话，我将接受去舞会的邀请。
If I knew her well, I would tell you about her.
如果我很了解她的话，我将告诉你关于她的事情。
2. 与过去事实相反
条件从句用过去完成时，主句用“would /should/ might / could + have +过去分词”, 如：
If you had been there last night, nothing would have happened.
如果你昨天晚上在那儿的话，就没有什么事情发生了。
If I had got up earlier, I would have caught the first bus.
如果我起得更早一些的话，就赶上头班车了。
3．与将来事实相反
条件从句用过去时或者“were to + 动词原形”或者“should+ 动词原形”，主句用“would （should/ might / could）+动词原形”, 如：
If it were Saturday tomorrow, we wouldn’t have an exam.
如果明天是周六的话，我们就不考试了。
If you were to visit the school tomorrow, you would see Professor Smith.
如果你明天去参观学校的话，你就会看到史密斯教授。
If it should rain tomorrow, the sports meet would be put off until next Friday.
如果明天下雨的话，运动会将被推迟到下周五举行。
【特别提示】
在虚拟条件句中，谓语动词按照“后退一步法”使用，即：与现在事实相反，从句中用一般过去时；与过去事实相反，从句中用过去完成时；与将来事实相反，从句中用过去将来时。
二、虚拟条件句中的省略与倒装
如果if虚拟条件句中有were, had, 或者should等词时，可以省略if，把这些词放在主语前，形成倒装句。如：
If I should meet her (Should I meet her), I would tell her.
如果我遇见她的话，我就告诉她。
If I were in your position (Were I in your position), I would do it better.
如果我在你的位置上，我会做得更好。
If they had made preparations (Had they made preparations), they would have succeeded.
如果他们做了准备的话，他们就已经成功了。
Grammar work语法专练
动词变形
用所给动词的适当形式填空。
1. —¬ If the factory ___________ (belong) to me, I ___________ (not sell) it.
— But it isn’t yours.
2. — If you ___________ (keep) the secret, nobody ___________ (know) it.
— I’m sorry for making such a mistake.
3. If the weather were to be (be) fine tomorrow, I ______ (go) for an outing with my parents.
4. ___________ (be) I you, I would think about this problem once again.
5. ___________ (have) I had time last night, I ___________ (go) to see this wonderful film.
完成句子
根据中文提示完成下列各句。
1. 如果你年轻五岁，你该怎么办？
What ___________ you ___________, if you ___________ five years younger?
2. 如果你开车更小心一点，就不会出这样的事故。
If you ______________________ your car more carefully, such a traffic accident _________________________________.
3. 如果明天下雾，我就不能开车去购物。
If it ___________ foggy tomorrow, I ______________________ my car to go shopping.
4. 如果明天天气转晴，我们就去野餐。
If it ______________________ clear up tomorrow, we ______________________ for a picnic.
5. 如果我是一个男孩，我当然会去参军。
If I ___________ a boy, I ___________ certainly join the army.
6. 如果你是我兄弟，你也会一样对我。
If you ___________ my brother, you ___________ treat me in the same way.
7. 如果我有你这样的姐姐会非常幸福的。
I ___________ ___________ very happy, if I ___________ an elder sister like you.
8. 如果我捡到了那只钱包，一定交给失主了。
If I ______________________ up the wallet, I _________________________________ it to its owner.
9. 万一明天下大雪，一切都将被改变。
If it ___________ snow heavily tomorrow, everything ___________ be changed.
10. 如果你那天没有抽烟，火灾就不会发生。
If you ______________________ that day, the fire _________________________________ out.
Grammar quiz语法小测
测一测
选择最佳答案。
1. He ______ you more help, even though he was very busy.
A. might have given B. might give C. should give D. may give
2. What would have happened ________ as far as the river bank?
A. Bob had walked B. if Bob should walk
C. had Bob walked D. if Bob walked
3. ________ I in your position, I would not accept the invitation.
A. Was B. Were C. Be D. Am
4. If my father ________ here the day after tomorrow, he ________ me at all.
A. came, can’t see B comes, couldn’t see
C. comes, couldn’t have seen D. came, couldn’t see
5. If it ________ to snow next week, I would not go to visit that mountain village.
A. is B. be C. were D. are
6. If it ________ rain this evening, I would not go to see this American film.
A. would B. should C. could D. might
7. __________ asked to do this, I would certainly do it in a different way.
A. Were I B. Am I C. If I am D. Was I
8. If he could help us, I am sure he ________. He’s always ready to help others.
A. should B. had C. would have D. did
9.________ her in time, she would have jumped into the river.
A. If I stopped B. Did I stop
C. If I didn’t stop D. If I hadn’t stopped
10. If I _________ ten years younger, I _________ out to try my luck.
A. am, would go B. was, will go C. were, would go D. were, would have gone
11. If you __________ my advice, you _________ such a serious mistake.
A. followed, can’t make B. followed, couldn’t have made
C. had followed, couldn’t make D. had followed, couldn’t have made
12. If I _________ that crowded bus yesterday morning, I _________ my purse with a lot of money in it.
A. didn’t take, couldn’t lose B. hadn’t taken, wouldn’t have lost
C. hadn’t taken, couldn’t lose D. didn’t take, can’t have lost
语法专练 (One possible version)
动词变形
1. belonged; wouldn’t sell 2. had kept; would have known 3. would go 4. Were 5. Had; would have gone