题目内容：

一个英语问题,关于only修饰状语
第一道题 it was only when i got home late in the evening that ___ what had happened to my brother
A.i knew B.i had known C.did i know D.had i known
这个是成都还是绵阳的二诊题,答案是选A,不倒装的原因解释为only不在句首
第二道题 it was announced that only when the fire was under control____to return to their homes
A.the residents would be permitted B.had the residents been permitted
C.would the residents be permitted D.the residents had been permitted
这个是江西08年的高考题,答案是选C,only也没有再句首啊,不要告诉我是因为一个是强调句一个是主语从句
就是only修饰状语位于句首倒装,那个句首的具体含义到底是什么,是非要在句子开头要大写,还是只要位于意义上的句首就可以了,比如就像第二题中主语从句的句首一样.还有一次我也遇到过,only是放在了but连接的并列句后面,也不算是真正位于句首大写了的那种,但还是倒装了的.
求解释- -,句首到底怎么定义啊

优质解答

第一句是一个强调句型,其中的only when i got home late in the evening 是被强调的部分,确实没有在句首,所以后面的不用倒装.
第二句中的that only when the fire was under control____to return to their homes是一个从句,相对独立,所以only when the fire was under control是位于这个从句的句首,复合倒装结构的要求.