do you know the person to whom I am talking.为什么不用who
问题描述：
do you know the person to whom I am talking.为什么不用who
答
who 既可以作主语,也可以作宾语.
但是当前面有介词时,只能用whom ,不能用 who .
本句中 to 是介词 ,所以只能用 whom .
实际上是 talk to whom ,宾语whom 提前了.