问题补充：
副词修饰动词不是放在动词后面吗?
一般情况是这样的,但也有个别放前面的,还有这个talk about 是词组,不能分,所以只有:
What does the passage mainly talk about
What does the passage talk about mainly?
两种.
What does the passage talk about
文章主要讲了什么?
mainly 修释的是'讲'
修释动词,自然要用副词.