By whom is the baby looked after?特殊疑问句,不是以特殊疑问词开头的吗?为什么这句话会以

通常by不移到句首也可以,比如：
The toy is made by a little girl. --> Whom is the toy made by?
但是 原句中动词短语 looked after 是以介词 after 结尾,如果by 不提到句首,读起来不顺.同样的道理,The old man is taken care of by his son. ---> By whom is the old man taken care of? 这样才通顺.
这和语法中提到的倒装不是一回事