疑问代词用来构成特殊问句,这个疑问代词可作主语,宾语,表语或定语.如
Who broke the window?
What shall we do now?
who is it
Which book do you want
关系代词是来引导从句的.如
what you said is important .
I want to know what is happening in our classroom.
Our problem is who can help me right now.
I can't decide which book I should choose.