Given this "debug isdn q921" output, what is the problem with the PRI?

Refer the exhibit.

Given this "debug isdn q921" output, what is the problem with the PRI?
A . Layer 1 is down on the controller.
B . PRI does not have an IP address configured on the interface.
C . Noting, the PRI is sending keepalives.
D . Layer 2 is down on the controller.

View Answer

Answer: D