Which of these is an advantage of the multizone model VCS with Prefix Dialing?

Which of these is an advantage of the multizone model VCS with Prefix Dialing?

A.
Location requests are only sent to the relevant zone

B.
Location VCS servers only need to know about the directory VCS and do not need to know about any other local VCS

C.
When adding a new zone, only the directory gatekeeper needs to be configured

D.
All gatekeepers know about all calls at times