问题
单项选择题
There is free firewall software available that can run on minimal hardware and provide a good level of (71) to your network.
A．protective
B．profectiog
C．protection
D．profection
答案
参考答案：C
解析：[分析] 免费的防火墙可以安装在很小的硬件上，对计算机网络提供高水平的保护。