同学你好，该知识点来自沪江网校《【Uni智能】雅思6.5分一站式VIP-初级起点【4月签约班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好，解答如下，希望能帮到你：
1. 如果指人的关系代词在定语从句中充当主语,用who不用whom.
如：Do you know the boy who is standing there?
2. 如果指人的关系代词在定语从句中充当动词/介词的宾语时,则用whom,或者who都可以.
如：Do you know the boy who/whom I was talking with? (who/whom充当介词with的宾语)
Do you know the boy who/whom I met just now? (who/whom充当met的宾语)
但是,如果指人的关系代词在定语从句中充当介词的宾语,且介词和该关系代词一并提前至定语从句句首时,则只能用whom,不能用who.
再如：Do you know the boy with whom I was talking?