1. [单选题]IP地址为：192.168.50.70，掩码为：255.255.255.248，则该IP地址所在子网的广播地址为（）
A. 192.168.50.32
B. 192.168.80.64
C. 192.168.50.96
D. 192.168.50.71
2. [多选题]Regarding the extended ping command; which of the statements below are true?(Select all valid answer choices)
A. The extended ping command is supported from user EXEC mode.
B. The extended ping command is available from privileged EXEC mode.
C. With the extended ping command you can specify the TCP and UDP port to be pinged.
D. With the extended ping command you can specify the timeout value.
E. With the extended ping command you can specify the datagram size.
3. [单选题]路由器当前的模式为“端口模式”，要退回到“特权模式”，应该使用的快捷键为（）
A. ctrl+b
B. ctrl+z
C. ctrl+c
D. ctrl+p
