1、(用作疑问代词)哪一个,哪一些
Which is my seat?哪个座位是我的?
2、(用做关系代词)那一个,那一些
He also had a gun with which to defend himself.他还有一把自卫用的枪。
3、（用作疑问形容词)哪一个,哪一些
Which university did you go to, Oxford or Cambridge?你上过哪所大学?牛津还是剑桥?
4、(用作关系形容词)这个,这些
The doctor told him to give up smoking, which advice he took.医生叮嘱他戒烟,他接受了这一忠告。
