计算机病毒是指能够侵入计算机系统并在计算机系统中潜伏、传播、破坏系统正常工作的一种具有繁殖能力的

A．指令

B．程序

C．设备

D．文件

When underway in a channel,you should keep to the（）.

A.middle of the channel

B.starboard side of the channel

C.port side of the channel

D.side of the channel that has the widest turns