单机挂车时，在区间被迫停车后的防护工作由机车乘务组负责，开车前应确认附挂辆数和制动主管__是否良好
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键盘、鼠标、扫描仪等属于__;显示器、打印机、绘图仪、音响等属于输出设备
Nowadays,weutilizeGMDSS（）
A. because there are many flaws of the previous radio communication system
B. because a conference was held in 1962
C. because Telestar was put into orbit
D. A and C are all right
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