You work as a network consultant at YourDomain .com. One of your clients wants to connect an IP network and a legacy communication system to the Public Switched Telephone network (PSTN).
What should you tell the client?

A.
Use Cisco VG248 Analog Phone Gateway.

B.
Use Cisco 7800 Series Media Convergence Server (MCS).

C.
Use Cisco CallManager.

D.
Use Survivable Remote Site Telephony (SRST).