执行返回指令，退出中断服务程序，这时返回地址来自( )。A．ROM区 B．程序计数

802.11b/g工作频率为（）GHz，802.11a工作频率为（）GHz

商业银行业务授权应适当、明确，一般采取书面形式；特殊情况下可以口头授权，事后补书面材料。

“一特四大”的关键在于什么？

家用中央空调噪音大吗？

Any computer, be it a large PC or a small embedded computer, is useless if it has no means to interact with the outside world. I/O communications for an embedded computer frequently happen over a bus called the ______.

A．I/O bus

B．Memory Bus

C．Device bus

D．Internal Bus