The police finally caught up with the man __the escaped prisoner.填who 还是whom?

题目

The police finally caught up with the man __the escaped prisoner.填who 还是whom?
书上的答案是B
A.whom they thought was
B.who they thought was
they thought he was a prisoner...he是宾语麼?
我还是不懂..
they thought the man was a prisoner...若he是宾语...倒过来不是the man whom they thought was a prisoner麼?为什麼用who呢??'
若 the man who was....的话是the man是主语所以用who,但插入了'they thought'又怎样理解呢??谢谢意

答案

警察最终抓住了那个他们认为是逃犯的人
who 指代的是the man,同时又是后面句子的主语
they thought 是个插入语,可以被省略为：如下
The police finally caught up with the man who was the escaped prisoner.
这样就容易理解些了吧