原句是：They ware talking about the girl.
talk 可做不及物动词，那么后面的about the girl就是修饰动词talk 的，修饰动词就是状语啊。
句子一 ：The book was written by Li Ming.
句子二 ：There are many interesting things in the book.地点状语
The book in which there are many interesting things was written by LiMing.
I forgot the day.
You came on the day.
合并：I forgot the day on which you came.
I can't see the reason.
He left me for the reason.
合并：I can't see the reason for which he left me.