1.纠正一个错误：他们不是先行词，而是关系代词 2.他们所引导的先行词都指人 3.当先行词在定语从句中作宾语时，who与whom都可用。

但最好用whom,如： The man with whom our teacher is talking is my father. =The man with who our teacher is talking is my father. 4.当先行词在定语从句中作主语时，用who,如： The man who is standing there is my father. 5.当先行词在定语从句中作定语时，用whose。

如： The man whose name is Peter is a actor.。