宾语从句,主语从句,定语从句who 1):可引导特殊疑问句;eg:Who is over there?(在那儿的那个人是谁?)
2): 可引导名词性从句(包括主语从句,宾语从句,表语从句,同位语从句),在句中做主语;主语从句eg:Who will do the job has not been decided yet;(还没决定谁去做那份工作); 同位语从句eg:The question who should do the job requires consideration(谁应该做这个工作的问题还需要考虑)。###ZHU:没找到宾语从句和表语从句的例子,不好意思。
3)可引导定语从句,做主语eg:Do you know the man who/that is standing by the window?(你认识那个正站在窗边的人吗?)
4)引导强调句型:It is I who/that am responsible for the project.(要对那件事负责的是我〈而不是其他人〉)who只能用于“人”。大概是这样。谢谢!~~~~~~~~~参考资料:大部分选自〈〈高中英语语法一本通〉〉本回答被提问者采纳