当学生 A 用两台 Star-R2624 路由器在做路由器广域网口连通实验时误将本端路由器 V.35 线缆的插头插倒了。结果发现 ping 直连的路由器不通,请问此时查看本端路由器的状态应该是?
A.A、Serial 0 is up, line protocol is up B.B、Serial 0 is up, line protocol is down C.C、Serial 0 is down, line protocol is down D.D、Serial 0 is down, line protocol is up