问题
单项选择题
Files can be lost or destroyed accidentally. Keep (74) copies of all data on removable storage media.
A．move
B．paste
C．backdown
D．backup
答案
参考答案：D
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Files can be lost or destroyed accidentally. Keep (74) copies of all data on removable storage media.
A．move
B．paste
C．backdown
D．backup
参考答案：D
2Cu + CO2↑的反应，下列说法正确的是 [ ]