在动力监控系统维护过程中，以下（）不属于软件系统的安全防护内容。
A.安装补丁程序
B.安装和设置防火墙
C.安装业务台软件
D.安装杀毒软件
参考答案：C
If you had helped him, he _________happy now. [ ]
A.is
B. would have been
C. Was
D. would be
冷作公差
