怎样判断定语从句中关系代词是作主语，宾语还是定语？

Question

如题所述

Answer 1

简单办法：
拿掉定语从句引导词，看从句中缺什么成分，关系代词就作什么成分。
例子：
He is the boy who likes play basketball.
who likes play basketball拿掉who，缺主语，who主语
He is the boy who I am looking for.
who I am looking for拿掉who，缺宾语，who宾语
He is the boy whose father is a teacher.
whose father is a teacher.拿掉whose，缺定语，whose定语

Answer 2

根据谓语判断定语从句中关系代词词性。