A technician arrives in Germany and discovers that when their PC is plugged into the outlet, nopower is received. Which of the following actions should the technician take to get the PC tooperate?（）

A、Change the BIOS settings to the local time

B、Adjust the voltage selector switch

C、Attach a 220 volt power strip from the current region to the PC

D、Attach a 120 volt battery backup power supply to the PC

You have been asked to use a 23-bit network mask to segment the network block 209.18.12.0, How many usable host address will there e per subnet?（）

A、510

B、1022

C、2046

D、8190

（）不属于系统安全的技术。

A、防火墙

B、加密狗

C、CA认证

D、防病毒

交换机（）是由于外部供电不稳定，或者电源线路老化或者雷击等原因而引起的。

A、电源故障

B、端口故障

C、模块故障

D、背板故障

计算机操作系统的主要功能是（　　）。

A、对计算机的所有资源进行控制和管理，为用户使用计算机提供方便

B、对源程序进行翻译

C、对用户数据文件进行管理

D、对汇编语言程序进行翻译

Which two statements are true about the rescue configuration file?（）

It must include a root password

It is roll back file number 50, and you can recover it by issuing rollback 50

It is created by issuing request system configuration rescue save

It is updated automatically when you commit