I've become good friends with several of the students in my school ______ I met in the English

问题描述:

I've become good friends with several of the students in my school ______ I met in the English
speech contest last year.答案是who,但是who也可以作宾语吗?

用who 或者whom 都可以.
who 既可以作主语也可以作宾语,whom 只能作宾语.可不可以讲一下为什么不能用which?