虚拟语气

一．虚拟语气在条件句中的用法:

    条件句有真实条件句和非真实条件句两种。

1. 在条件句中的应用

条件句可分为两类，一类为真实条件句，一类为非真实条件句。

A 真实条件句

真实条件句用于陈述语气，假设的情况可能发生。

时态关系

句型：条件从句       主句

      一般现在时     shall/will+动词原形

If he comes, he will bring his violin.

典型例题

The volleyball match will be put off if it_______.

A. will rain    B. rains    C. rained    D. is rained

答案B。真实条件句主句为将来时，从句用一般现在时。

注意：

（1）       在真实条件句中，主句不能用be going to表示将来，该用shall, will.

（2）       表示真理时，主句谓语动词不用shall(will)+动词原形，而直接用一般现在时的动词形式。

B 非真实条件句

 非真实条件句所表的假设则是不可能或不大可能发生或实现的，句中的条件从句与结果主句皆用虚拟语气。

1. 表示跟现在事实相反

  从句的谓语用动词的过去式（be的过去式用were），构成If I （we, you, he, they）＋动词过去式的形式；

If I were you, I should (would, could, might)tell him the truth.

 If he had time, he would (could, might) go with you.

2. 与过去的事实相反

   从句的谓语用had＋过去分词，构成If I (we, you, he, they)＋had＋过去分词的形式；主句的谓语用should（第一人称）/would（第二、三人称）/could/might have ＋动词过去分词。

如果你仔细一点， 这个错误是可以避免的. 例如：

If I had time last night, I should have come to see you.

He would never have behaved like that if he had had a good education.

3. 与将来事实相反

    从句的谓语用If I (we, you, he, they) ＋动词过去式或were to do 或should do 形式，主句谓语用should（第一人称）/would（第二、三人称）/could/ might ＋动词原形。例如：

If he were to come, what should we say to him.

If we climbed to the top of the mountain, should we get a good view?

4. If从句中若含有should, had 或者were，那么就可以把它们放在句首，与主语颠倒形成倒装，但动词过去式不可以与主语倒装。例如：

Were he here, he would come to help us.

Had you been here just now, you would have met her.

5. 当条件状语从句表示的行为和主句表示的行为所发生的时间不一致时，被称为“错综时间条件句”，动词的形式要根据它所表示的时间作出相应的调整。例如：

If he had set out earlier, he would be home now.

If I were not busy, I would have come.

6. 用介词短语代替条件状语从句。常用的介词由with, without, but for等。例如：

We couldn’t have finished the work ahead of time without your help. (＝if we hadn’t got your help)

7. 含蓄条件句

有时为了表达的需要，在虚拟语气中并不总是出现if引导的条件句，而通过其他手段代替条件句。例如：

I was ill that day. Otherwise, I would have taken part in the sports meet.（副词）

He telephoned to inform me of your birthday, or I would have known nothing about it .（连词）