北师大版高中英语必修5 Unit15 lesson 1：

虚拟语气（与过去事实相反）

一、表示过去非真实的情景，和对过去事实并未发生的事情提出假设，使用以下结构。

If + Past perfect, would/could/might + 不定式完成式

If you had taken my advice yesterday，you wouldn't have failed in the exam.

二、有时条件从句中的动作和主句中的动作发生的时间不一致，这时动词的形式要根据它所表示的时间加以调整。

If you had listened to the doctor, you would be all right now. 如果你当初听了医生的话，身体现在就好了。

三、如果虚拟条件从句中有had (were/should), 可以把if省略，把这几个词放到主语之前，构成主谓倒装。

Had I met Li Hua, I could had told him. 如果我碰见了李华，我就告诉他了。

四、有时假设的情况并不用条件从句表示出来，而是通过介词短语等其它形式表达。

But for your help (If it hadn’t been for your help) I couldn’t have done it.

假设的情况有时可以通过上下文或其他方式表现出来。

I was busy that day. Otherwise I would have gone there with them.

(= If I hadn’t been busy that day, I would have gone there with them.)

I would have finished the work, but I have been ill.

(= If I hadn’t been ill, I would have finished the work.)

五、练习

1.If the parents ______ (arrive)at the hospital earlier after the accident, the child would have been saved.

2. I didn’t see your sister at the meeting. If she _______(come), she would have met my brother.

3. What would have happened, _____ as far as the river bank?

  A. Bob had walked farther               B. if Bob should walk farther

  C. had Bob walked farther               D. if Bob walked farther

4. _______the exam, he would have attend a college.

  A. If he passed     B. Had he passed    C. Were he passed     D. If he should pass

5. If you _____ him yesterday, you _____ what to do now.

  A. asked … would know        B. had asked … would have known

  C. asked him … know              D. had asked … would know

6. I went by plane; otherwise I ____ much longer time.

  A. could take    B. would take    C. will have taken  D. would have taken

7. Without your help, we ____ such rapid progress.

  A. couldn’t make            B. wouldn’t make

  C. will not have made        D. wouldn’t have made

8. I'd rather you ________(post) the letter yesterday.

9. We wish you _________(come) to our English evening last week.

答案：1.had arrived  2. had come  3. C  4.B    5. D   6.D   7.D  8.had posted  9.had come