设选课表的结构为：(学号、课程号、成绩)，其中学号+课程号为主键。要从选课表中统计每个学生选修的课程门数，应使用的SELECT-SQL语句是______。

A. Tunnels are initiated by the LAC

B. Tunnels are initiated by the LNS

C. By default, subscriber authentication occurs on the LNS

D. By default, subscriber authentication occurs on the LAC

A.Requires only one tunnel switching license.

B.Requires two licenses, one for inbound and one for outbound sessions.

C.Enabled automatically when the BSR is configured as an LAC and LNS.

D.Aids in L2TP tunnel scaling.

A. Traffic is clear text

B. Traffic is encrypted

C. They are initiated by the LNS

D. They are initiated by the LAC

A. l2tp tunnelling

B. l2tp tunnel switching

C. l2tp tunnel-switching

D. enable l2tp tunnel switching

A.show subscriber

B.show l2tp tunnel

C.show l2tp session

D.show tunnel session

A. LNS IP address is defined.

B. LAC IP address is defined.

C. Virtual-router vr1 sends and receives L2TP traffic.

D. Virtual-router vr1 is the authenticating virtual-router.

E. This command is performed on the LNS.

A.Traceroute transmits ICMP echo-request packets.

B.Traceroute transmits UDP packets.

C.Traceroute receives ICMP echo-reply packets.

D.Traceroute receives ICMP port-unreachable packets.

A.l2tp tunnel test anyone@isp1.com

B.test l2tp session anyone@isp1.com

C.test l2tp tunnel anyone@isp1.com

D.tunnel l2tp test anyone@isp1.com

Which of the following item was NOT mentioned about the restaurant？

A．The price.

B．The service.

C．The interior design.

D．The service.