Which feature is automatically enabled when a voice VLAN is configured, but not automatically disabled when a voice VLAN is removed?

A.
portfast

B.
port-security

C.
spanning tree

D.
storm control

Explanation:
Voice VLAN Configuration Guidelines
·You should configure voice VLAN on switch access ports. ·The voice VLAN should be present and active on the switch for the IP phone to correctly communicate
on the voice VLAN. Use the show vlan privileged EXEC command to see if the VLAN is present (listed in the display).
·The Port Fast feature is automatically enabled when voice VLAN is configured. When you disable voice VLAN, the Port Fast feature is not automatically disabled.

http://www.cisco.com/en/US/docs/switches/lan/catalyst2950/software/release/12.1_22_ea11x/conf iguration/guide/swvoip.html