Our teacher told us _______ too much time surfing the internet. It's bad for our health. [ ]

A. not to cost

B. not to spend

C. not to pay

D. not to take

处理器执行的指令被分成两类，其中有一类称为特权指令，它只允许( )使用。

A．操作员

B．联机用户

C．操作系统

D．目标程序