问题
单项选择题
（） is not a physical wall, but a lot of virtual data to protect the computer network.
A. Date wall
B. Date channel
C. Database
D. Firewall
答案
参考答案：D
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（） is not a physical wall, but a lot of virtual data to protect the computer network.
A. Date wall
B. Date channel
C. Database
D. Firewall
参考答案：D