路由器A的配置如下 Quidway#SHOW RUN Now create configuration... Current configuration !

路由器A的配置如下 Quidway#SHOW RUN Now create configuration... Current configuration ! ! interface Ethernet0 ip address 10.2.1.1 255.255.0.0 ! interface Serial0 encapsulation ppp backup interface Serial 1 ip address 2.1.1.1 255.0.0.0 ! interface Serial1 encapsulation ppp ip address 3.1.1.1 255.0.0.0 ! interface Serial2 flowcontrol normal async mode dedicated encapsulation ppp ! Exit Router rip ! End 路由器B的配置如下 Quidway#SHOW RUN Now create configuration... Current configuration ! ! interface Ethernet0 ip address 10.1.1.1 255.255.0.0 ! interface Serial0 encapsulation ppp backup interface Serial 1 ip address 2.1.1.1 255.0.0.0 ! interface Serial1 encapsulation ppp ip address 3.1.1.1 255.0.0.0 ! interface Serial2 flowcontrol normal async mode dedicated encapsulation ppp ! Exit Router rip ! End 下述说法正确的是

A、备份功能可以正常使用 B、备份功能不能正常使用 C、两端可以正常互联 D、两端不能正常互联

请帮忙给出正确答案和分析，谢谢！