When a WAN link problem occurs, it takes over three minutes for IP phones to become registered with the SRST gateway. What is the most likely cause of this?

A.
The WAN link is bouncing.

B.
The keepalive timer in the SRST gateway is set too long.

C.
Each phone has a list of two alternate Cisco Unified CallManager systems, and it tries to register with each before registering with the SRST gateway.

D.
The SRST gateway is an MGCP gateway, and it must stop the MGCP process and switch over to the default H.323 process to initiate the SRST process.