Which method does a connected trunk port use to tag VLAN traffic?

Which method does a connected trunk port use to tag VLAN traffic?
A . IEEE 802 1w
B . IEEE 802 1D
C . IEEE 802 1Q
D . IEEE 802 1p

Answer: C

Explanation:

IEEE 802.1Q is the networking standard that supports virtual LANs (VLANs) on an Ethernet network. When a frame enters the VLAN-aware portion of the network (a trunk link, for example), a VLAN ID tag is added to represent the VLAN membership of that frame. The picture below shows how VLAN tag is added and removed while going through the network.

http://www.cisco.com/c/en/us/support/docs/lan-switching/8021q/17056-741-4.html