The Acme Anvils Company is a large enterprise with many office sites. The company is planning to add IP videoconferencing to the existing IP telephony network. It has been determined that an MCU will be placed in each site. External participants in videoconferences will dial in using DID to reach the conference MCUs. Internal participants will dial the proper extension numbers for conferences. What does Cisco recommend for the videoconferencing gateway placement and the IP-videoconferencing dial plan?

A.
a single videoconferencing gateway with a single zone prefix for all MCUs

B.
a single videoconferencing gateway, with the MCUs at each site having a separate zone prefix that is independent of the area code

C.
a videoconferencing gateway in every site, with an MCU zone prefix for each site that is independent of the area code

D.
a videoconferencing gateway in every site, and the MCU zone prefixes matching the local area code

E.
a videoconferencing gateway in every site, and all the MCUs placed in a single zone prefix