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

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.

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