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口路由器V.35线缆的插头插倒了。结果发现PING直连的路由器不通，请问此时需要查看路由器的状态应该是（）

• A、Serial 0 is up，line protocol is down
• B、Serial 0 is down，line protocol is down
• C、Serial 0 is down，line protocol is up
• D、Serial 0 is administratively down，line protocol is