Within a distributed call processing environment, what can you use to achieve call admission control

Within a distributed call processing environment, what can you use to achieve call admission control across the WAN?

A.
You can use a 720VXR to diversify the IPN1 traffic.

B.
You can use a CiscoWorks RME package to keep lines clear.

C.
You can use a gatekeeper.

D.
You can use a H.333 Line card.