问题
单项选择题
Files can be lost or destroyed accidentally. Keep （）copies of all data on removable storage media.
A．backup
B．back
C．black
D．backdown
答案
参考答案：A
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Files can be lost or destroyed accidentally. Keep （）copies of all data on removable storage media.
A．backup
B．back
C．black
D．backdown
参考答案：A