选择during the Olympic Games many people served as volunteers,( )were young collegduring the Olympic Games many people served as volunteers,( ) were young college students.most of them?most of which?most of whom?most of what?

问题描述:

选择during the Olympic Games many people served as volunteers,( )were young colleg
during the Olympic Games many people served as volunteers,( ) were young college students.
most of them?
most of which?
most of whom?
most of what?

B,非限制性定语从句,which指代前面提到的volunteers