Which connection method is best for these two new customers?

The corporate WAN has been extended to two newly acquired sites and it includes gatekeeper support. Each site has a Cisco CallManager and an H.323 gateway
that allows connection to the PSTN. Which connection method is best for these two new customers?

A.
H.225 trunk (gatekeeper-controlled)

B.
intercluster trunk (non-gatekeeper controlled)

C.
SIP trunk

D.
intercluster trunk (gatekeeper-controlled)