if 引导的非真实性条件状语从句 即 虚拟语气
通过动词形式的变化来表示说话人对发生的动作或存在的状态所持的态度或看法的动词形式称为语气。.英语中的语气分三种：陈述语气、祈使语气、虚拟语气。虚拟语气表示说话人所说的话不是事实，而是一种祝愿，建议，与事实相反的假设或实际可能性不大的情况等（即非真实的假设）。
If 引导的条件状语从句分为真实和非真实条件句（虚拟条件句）。真实条件句表示在假设的条件下，有可能实现的情况。非真实条件句表示的是假设的或实际可能性不大的情况，故采用虚拟语气。
If he doesn’t hurry up, he will miss the bus.( 真实条件状语) If he was free, he asked me to tell stories.（真实条件状语） If I were you, I would go at once.（非真实条件状语从句） If there was no air, people would die.（非真实条件状语从句） 1）非真实条件句中虚拟语气的基本形式。 假设类型 条件从句的动词 结果主句的动词
与现在事实相反 动词过去式（be只用were） would/should/could/might + 动词原形
与过去事实相反 had+过去分词 would/should/could/might + have + 过去分词
与将来事实相反 动词过去式/(should/were to)+动词原形 would/should/could/might + 动词原形
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①与现在事实相反
If I had time, I would go for a walk.
如果我有时间，我就会去散步。(实际情况：我现在没有时间，也不会去散步。)
If I were you, I would take an umbrella.
假如我是你的话，我会带上雨伞。(事实上我不可能是你。) I would say no if someone asked me to be in a movie. 假如有人请我当电影演员，我会表示拒绝。(事实上现虚拟语气专项练习
1．Were it not for the snowy weather, we __________all right. A. would be B. would have been C. were D. may be 2. ________more careful, his ship would not have sunk. A. If the captain were B. Had the captain been
C. Should the captain be D. If the captain would have been 3. If he _________ me tomorrow, I would let him know. A. should call B. should not have been able C. were not able D. are not able
4. If you asked your father, you ______________ permission. A. may get B. might get C. should have called D. maybe get
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5. _____________today, he would get there by Friday. A. Would he leave B. was he leaving C. Were he to leave D. If he leaves
6. ______I you, I would go with him to the party. A. Was B. Had been C. Will be D. Were
7. The millions of calculations involved, had they been done by hand, __________all practical value by the time they were finished.
A. could lose B. would have lost C. might lose D. ought to have lost
8. Had Paul received six more votes in the last election, he ________our chairman now.
A. must have been B. would have been C. were D. would be
9. If you ________________Jerry Brown until recently, you'd think the photograph on the right was strange. A. shouldn't contact B. didn't contact C. weren't to contact D. hadn't contacted
10. ____________he English examination I would have gone to the concert last Sunday
A. In spite of B. But for C. Because of D. As for
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