二、错综条件句

1.从句表示过去，主句表示现在

If I had worked hard at school，I would be an engineer，too.

如果我在学校学习刻苦的话，我现在也会是工程师了。

If they had informed us，we would not come here now.

如果他们通知过我们的话，我们现在就不会来这里了。

2.从句表示现在，主句表示过去

If he were free today，we would have sent him to Beijing.

如果他今天有空的话，我们已经派他去北京了。

If he knew her，he would have greeted her.要是他认识她的话，他肯定会去问候她了。

3.从句表示将来，主句表示过去

If I were not to prepare for my experiment this afternoon，I would have gone to see the film with you last night.如果不是今天下午我要准备实验，昨晚我就和你去看电影了。

If she were leaving，I would have heard about it.如果她要走，我早就会听说了。