单项选择题
A firewall is a (1) system designed to (2) an organization’s network against threats.
A.operating B.programming C.security D.service
A.0.93 B.0.95 C.0.97 D.0.99
A.分析数字系统层 B.非对称数字线 C.非对称数字用户线 D.异步数字系统层