How should CAC be implemented?

In a centralized call-processing solution, there are five sites connected through an IP WAN. To optimize the utilization of the IP WAN, CAC needs to be implemented.

How should CAC be implemented?
A . Use a gatekeeper to control allocated bandwidth properly.
B . Use locations CAC with a single location.
C . Use a gatekeeper and Cisco Unified Border Element to provide CAC to sites that use a combination of SIPand MGCP gateways.
D . Use a gatekeeper to only control those locations that use
E . 323 gateways and a Cisco Unified BorderElement to control those sites that use MGCP or SIP gateways.
F . Use locations CAC with five locations in addition to Hub none.

Answer: E