How can the activation status of DNS services be changed?

A.
DNS activation can only be changed by reinstalling Cisco Unified CallManager.

B.
DNS activation can be changed at any time.

C.
DNS activation is on by default and can only be turned off at installation; once DNS activation has been turned off, the system must be reinstalled to turn it back on.

D.
DNS activation is on by default and cannot be changed, but leaving the DNS server addresses and domain name blank disables the service.