主从句

构成

时态 if虚拟条件句 主句 与现在事实相反 if＋主语＋动词过去式 主语＋would/should/could/might＋动词原形 与过去事实相反 if＋主语＋had＋过去分词 主语＋would/should/could/might＋have＋过去分词 与将来事实相反 if＋主语＋ 主语＋would/should/could/might＋动词原形 　　

　　If I were a bird, I could fly.

　　如果我是一只鸟的话，我就能飞了。

　　If we had started earlier, we would not have missed the train.

　　如果我们早点出发，就不会错过这列火车了。

　　If he shouldn't come tomorrow, we should put off the meeting till next Monday.

　　要是他明天来不了，我们将把会议推迟到下周一。

　　[即时演练1]　用所给动词的适当形式填空

　　①(2017·北京高考改编)If the new safety system had_been_put (put) to use, the accident would never have happened.

　　②(湖南高考改编)Sorry, I am too busy now, if I had (have) time, I would certainly go for an outing with you.　

　　③If I were (be) you, I would_go (go) to see the film Lost on Journey.

　　④If you had_worked (work) hard last year, you would_have_passed (pass) the test.

⑤If she should_come/came/were_to_come (come) tomorrow, I would_ask (ask) her for help.