在一个通用串行总线接口上最多可以接入多少个USB设备（）。
A.32
B.64
C.127
D.255
参考答案：C
This is a _____ book that you may _____ in daily English study. [ ]
A. referring; refer to
B. referring; refer
C. reference; refer to
D. reference; refer
用于对重要事项或重大行动作出安排的文件，称为()。
A．条例
B．决定
C．指示
D．命令
