一台MSR 路由器通过广域网接口连接到Internet,在该MSR 路由器上看到如下接口显示信息: Mp-group1 current state: UP Line protocol current state: UP Description: Mp-group1 Interface The Maximum Transmit Unit is 1500, Hold timer is 10(sec) Internet Address is 172.16.1.100/24 Primary Link layer protocol is PPP LCP opened, MP opened, IPCP opened Physical is MP, baudrate: 64000 bps 那么对如上显示信息分析正确的是_ A. 该接口使用的物理电缆为MP 电缆 B. 该接口封装的链路层协议为PPP C. 该接口Mp-group1 至少包含了两个物理接口 D. 该接口运行的网络层协议为IP