Which one of these statements is true when considering the design of voice video service for the campus network?

A.
Access layer switches should support 802.1Q trunking and 802.1p for Layer 2 ports with IP phones connected.

B.
Combining voice and data and a single VLAN simplifies QoS trust boundaries, VLAN access control and ease of management.

C.
Data devices will also require access to priority queues via packet tagging.

D.
Fixed network delays (serialization, propagation, and so on) are generally unpredictable and more difficult to calculate than variable network delays.

Explanation:
802.1Q & 802.1P are required for Vlan tagging & prioritizing voice frames.
Link:
http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_25_sec/configu ration/guide/swvoip.html