Which technique allows specific VLANs to be strictly permitted by the administrator?

Which technique allows specific VLANs to be strictly permitted by the administrator?
A . VTP pruning
B . transparent bridging
C . trunk allowed VLANs
D . VLAN access-list
E . L2P tunneling

Answer: C

Explanation:

By default, a trunk port sends traffic to and receives traffic from all VLANs. All VLAN IDs, 1 to 4094, are allowed on each trunk.

However, you can remove VLANs from the allowed list, preventing traffic from those VLANs from passing over the trunk. To restrict the traffic a trunk carries, use the "switchport trunk allowed vlan remove vlan-list" interface configuration command to remove specific VLANs from the allowed list.

Reference: http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/release/12.1_13_ea1/confi guration/ guide/swvlan.html