Your Cisco Unified Wireless IP Phones 7921G and 7925G are associated with the VoWLAN at your branch office. When they attempt to place a call, the call fails to go through and you receive a fast busy tone. What is the issue?

A.
The wireless phones failed to register with the Cisco Unified Communications Manager cluster.

B.
The Cisco Unified Communications Manager cluster invoked CAC to preserve IP WAN voice bandwidth.

C.
The local gateway rejected the call because of high IP WAN utilization.

D.
Automatic alternate routing has been invoked.