Refer to the exhibit. A user at BR1 is on a call to the PSTN through the PRI interface on the local
H.
323 gateway. The IP WAN has just failed and the call has been dropped. 
What is causing the call to be dropped?
A.
The H.323 gateway has lost the D channel on the PRI.
B.
SRST hasn’t been configured on the BR1 gateway.
C.
The no h225 timeout keepalive command has not been configured on the gateway.
D.
The IP phone hasn’t registered with SRST.