Not until the war was over _______ to school.

A．that the children could go

B．the children couldn’t go

C．could the children go

D．the children could go

一个典型的网络操作系统一般具有______的特征，也就是说，它应当独立于具体的硬件平台，支持多平台，即系统应该可以运行于各种硬件平台之上。