During the last few years, it has been realized that maintenance of programs is more expensive than development, so reading of programs by humans is as important as（）them.

单项选择题Without systems software, application software in a computer is（）

A．nouse
B．useful
C．useness
D．useless

单项选择题连接打印机不能使用（）

A．RS-232C接口总线
B．IEEE-1284接口总线
C．CENTRONIC接口总线
D．AGP接口