单项选择题

Files can be lost or destroyed accidentally. Keep（）copies of all data on removablestorage media.

A．backup
B．back
C．black
D．backdown

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单项选择题
In（）programming, the user determines the sequence of instructions to be executed, not the programmer.

A．top-down
B．structure
C．data-driven
D．event-driven
单项选择题
The（）is a collection of computers connected together by phone lines that allows for the global sharing of information.

A．interface .
B．Internet
C．LAN
D．WWW
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