ask a question of grammar?

题目

ask a question of grammar?
the one which/that / who begins to talk is nervous.which hat and who which is correct?
and why?

答案

"who"
who引导了一个定语从句,其修饰限定了“the one”即开始讲话的人,因为修饰的是人,而且又作为定语从句中的主语,所以用who