3、混合条件句

主句与从句的动作发生在不同的时间，这时主，从句谓语动词的虚拟语气形式因时间不同而不同，这叫做混合条件句。
If you had asked him yesterday, you would know what to do now.
（从句与过去事实相反，主句与现在事实相反。）
If it had rained last night ( 过去 ), it would be very cold today ( 现在 ).

4、虚拟条件句的倒装

虚拟条件句的从句部分如果含有 were, should, 或 had, 可将 if 省略，再把 were, should 或 had 移到从句句首，实行倒装。
Were they here now, they could help us.
=If they were here now, they could help us.
Had you come earlier, you would have met him
=If you had come earlier, you would have met him.
Should it rain, the crops would be saved.
=Were it to rain, the crops would be saved.
注意：
在虚拟语气的从句中，动词 'be' 的过去时态一律用 "were" ，不用 was ， 即在从句中 be 用 were 代替。
If I were you, I would go to look for him.
如果我是你，就会去找他。
If he were here, everything would be all right.
如果他在这儿，一切都会好的。
典型例题
_____ to do the work, I should do it some other day.
A. If were I B. I were C. Were I D. Was I
答案 C. 在虚拟条件状语中如果有 were, should, had 这三个词，通常将 if 省略，主语提前 , 变成 were, should, had + 主语的形式。但要注意，在虚拟条件状语从句中，省略连词的倒装形式的句首不能用动词的缩略形式。如我们可说 Were I not to do., 而不能说 Weren't I to do.