Voice over Internet Protocol (VoIP) is a general term for a family of transmission technologies for delivery of voice communications over IP networks such as the Internet or other packet-switched networks. A VoIP phone having a built-in hub is plugged into a single network using both the hub port and the phone port. Because of the increasing traffic, the network becomes very slow. What can prevent this problem happening?

A.
Trunking

B.
Port mirroring

C.
VLANS

D.
Spanning tree