2、(用做關係代詞)那一個,那一些
He also had a gun with which to defend himself.
他還有一把自衛用的槍。
3、（用作疑問形容詞)哪一個,哪一些
Which university did you go to, Oxford or Cambridge?
你上過哪所大學?牛津還是劍橋?
4、(用作關係形容詞)這個,這些
The doctor told him to give up smoking, which advice he took.
醫生叮囑他戒菸,他接受了這一忠告。