We must do whatever we can to _____ the river being polluted any more.  [ ]

A. separate        

B. keep            

C. prevent          

D. guard

根据图1-23的配置，补充完成下面路由器的配置命令：
Router (config) #interface (3)
Router(config-if)#ip address 10.10.1.1 255.255.255.0
Routef(config-if)#no shutdown
Router(config-if)#exit
Router(config)#interface (4)
Router(config-if)#ip address 192.168.1.1 255.255.255.0
……
Router(config)#interrace (5)
Router(config-if)#ip address 10.10.2.1 255.255.255.0
……