同学你好，该知识点来自沪江网校《新概念英语第二册【随到随学班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好~

if条件句中如果有were，should，had，可以省去if，并使用倒装语序。

在虚拟条件句中，有时可以将引导虚拟条件句的连词 if 省略，但此时应用倒装句型，
即将从句中的were, should, had 等提到句首。
如：
如果她在这里，她也同意的。
If he were here, she would agree too.
→Were she here, she would agree too.

假若明天下雨，我们只好推迟这场比赛。
If it should rain tomorrow, we should have to put off the match.
→Should it rain tomorrow, we should have to put off the match.


注意，如果条件从句的谓语为否定式，其中的否定词not应置于主语之后，而不能与were, should, had 等缩略成Weren’t, Shouldn’t, Hadn’t而置于句首。

我如不是警告了你，你就可能丧命了。
正：If I hadn’t warned you, you could have been killed.
正：Had I not warned you, you could have been killed.
误：Hadn’t I warned you, you could have been killed.

另外，有时省略if后提前到句首的had可能不是助动词，而是实义动词。如：
Had I time, I would go with you. 假如我有时间，我就同你们一起去。
句中的had不是构成过去完成时的助动词，而是表示“有”。
如果不省略if，其完整形式为：If I had time, I would go with you.

祝学习进步~