Who is going to teach us maths next term? 下学期谁将教我们数学? (主语)
Whom are you talking about? 你们在谈论谁? (宾语)
Who is the young man over there?那边的那个年轻男子是谁?(表语)
Whose bag is that?那是谁的包? (定语)
Which one do you like,this one or that one? 你喜欢哪一个,这个还是那个?
which表示在一定范围内的选择,
而what则没有这种限制。