only when the war was over was he able to get back to work?其中为什么会有was,这是什么语法?

题目

only when the war was over was he able to get back to work?其中为什么会有was,这是什么语法?
类似的还有：the supervisor could have prevented the accident had he known it beforehand.这里为什么会出现had?

答案

嗯,楼上的人说的对,第二句就是所谓的部分倒装:在虚拟语气中,若非真实条件句省略if,那么必须将主句中的were或had或should等助动词和主语位置颠倒形成的部分倒装.当然这一句中的if意为如果.你只要记住看见助动词提前,...