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
单项选择题 （） is meant to provide facility for customer s need or inquiry and arrange it.
单项选择题 Saving or reducing expenditure in business is（）
单项选择题 Re-handling can save cost and improve service, Is it true or not? （）
