1. 虚拟条件句表示与现在事实相反的假设或现在不可能存在的情况时，条件从句谓语常用动词过去式（be动词的过去式用were），主句谓语用"would / should / could / might +动词原形"。如：

　If I were you, I would / should / could / might help him.

　If I had the book at hand, I would / should / could / might read the passage to you.

2. 虚拟条件句表示与过去事实相反时，条件从句谓语常用过去完成时，主句谓语常用"would / should / could / might have +过去分词"。如：

If you had worked harder, you would / should / could / might have passed your exams.

3. 虚拟条件句表示与将来事实相反时，条件从句谓语常用动词的过去式（be动词的过去式用were），should +动词原形或were to +动词原形，主句谓语用would / should / could / might +动词原形。如：

　If you lived there for a while, you'd change your mind about that place.

　If he should / were to come, what should we say to him?

【即学即练】

选用括号内合适的内容补全下面句子。

1. If I ________ (am, was, were) you, I would not play tennis.

2. If you wait a minute, I ________ (will, would) go with you.

3. You would have slept much better if you ________ (had taken, took) your medicine.

4. The teacher will not be happy if we ________ (will forget, forget) our homework again.

5. If Tom ________ (studied, had studied) the new words, he could get a good mark in the English test.

6. If we had seen the film, we ________ (wouldn't have, hadn't) bought the DVD.

7. If he ________ (fail, were to fail) in the experiment this time, he would try again.

答案

【即学即练】

1. were 2. will 3. had taken

4. forget 5. studied 6. wouldn't have 7. were to fail