Consider the following customer attributes and choose the correct IP telephony call processing model:
– a large campus that spans two PSAP areas
– a single group of buildings connected via fiber optics
– data VPNs that support multiple contractors and suppliers
– a fully developed three-tier network hierarchy
– connectivity to two different service providers for Internet access

A.
single-site call processing

B.
centralized call processing

C.
hybrid call processing

D.
distributed call processing