Refer to the exhibit.
interface GigabitEthernetl/0/4 description HQ Phone 1 switchport access vlan 10 switchport voice vlan 110 spanning-tree portfast
An IP phone that is connected through a Cisco Catalyst 3750 Series Switch is failing to register with Cisco Unified Communications Manager. When the user presses the settings button on the phone, the Operational VLAN ID shows a blank entry. What is the most likely cause for this issue?

A.	The switch may not be supplying inline power.
B.	The spanning tree portfast command needs to be removed.
C.	The trunk encapsulation is missing. The trunk must be configured for dot1.Q.
D.	Cisco Discovery Protocol is disabled on the switch.
E.	The Operational VLAN ID of the phone always shows as blank. The Admin. VLAN ID should be 110.