怎么判断that which whom 在定语从句中是作主语还是作宾语

一.定语从句的关系代词 Which的用法:若先行词指物则代替先行词在定语从句中充当主语或宾语.This is the pen which was given by my friend.先行词 指物代替先行词在定语从句中充当主语This is the pen which my frie...