Refer the exhibit.

Two routers are connected using GRE through a WAN link. Your syslog server is logging
the given error message. What is a possible reason for the errors?

A.
The loopback interface is configured as the source of the tunnel

B.
The connection is experiencing WAN link flapping

C.
The tunnel key is misconfigured

D.
Secondary addresses are being used on the physical interface

E.
The tunnel source and destination are advertised through the tunnel itself