What is the function of Cisco Unified CallManager Regions?

A.
to assign directory numbers to devices as they connect to the IP telephony network

B.
to implement call admission control in a centralized call processing deployment

C.
to define the time zones for devices connected to Cisco Unified CallManager

D.
to specify the codec used for audio and video calls

E.
to provide alternate call routing when the primary call path is unavailable