Which of the following deployment scenarios will be most suitable for a customer that requires telephony feature transparency, requires high availabilityand has two sites with 3000 IP phones connected via a low-delay connection?

Which of the following deployment scenarios will be most suitable for a customer that requires telephony feature transparency, requires high availabilityand has two sites with 3000 IP phones connected via a low-delay connection? Select exactly 1 answer(s) from the following:
A. intermedia engine solution
B. multisite WAN with centralized call processing
C. clustering over the IP WAN
D. multisite WAN with distributed call processing