An endpoint has a SIP trunk configured between Cisco Unified Communications Manager (CUCM) and a Cisco VCS cluster. When a call is made from a Cisco TelePresence System EX60 that is registered to the Cisco VCS to a Cisco IP Phone 9971 that is registered to CUCM, it rings. But upon picking up the call, a busy tone is heard.
What should be checked to resolve this issue?
A . CUCM zone on the Cisco VC
C . SIP trunk and phone region settings.
D . SIP trunk registration.
E . authentication on the SIP trunk.
Answer: B