Endpoints are configured for both H.323 and SIP using the same URI and Cisco VCS settings, but the endpoints register only as H.323 endpoints. What is causing this issue?

A.	A firewall is blocking all traffic from the endpoints to the Cisco VCS.
B.	The Cisco VCS has no SIP domains configured.
C.	The Cisco VCS is blocking the endpoints because of duplicate ID entries.
D.	The endpoints do not have the SIP option key installed.
E.	SIP does not work, because SIP is used for Cisco Unified Communications Manager registration only.