Many students were watching the story of the heroes from Changjiang University on TV, ________ moved to tears.

A．all of them

B．all of whom

C．all of that

D．all of which

操作系统主要功能是对系统的资源进行有效管理，包括处理机管理、存储器管理、I/O设备管理、作业管理和______。