单项选择题
A.部站备份路由B.省站备份路由C.分中心至收费站备份路由D.部站和省站备份路由
A.ping 10.255.7.7B.ping 10.255.7.8C.ping 10.254.7.7D.ping 10.254.7.8
A.60GB.100GC.140GD.300G