采用两片中断控制器8259A级联后，CPU的可屏蔽硬中断源能扩大到( )。
A．64个 B．32个 C．16个 D．15个
参考答案：D
My life a lot in the last few years. [ ]
A. change
B. changed
C. has changed
D. have changed
成本率就是成本毛利率。( )
