Which is the most important issue to be aware of when bulk assigning user licensing for presence users?

Which is the most important issue to be aware of when bulk assigning user licensing for presence users?

A.
Enable Cisco Unified Presence licensing before enabling Personal Communicator.

B.
All users must be configured before enabling Cisco Unified Presence and Cisco Unified Personal Communicator licensing.

C.
Cisco Unified Presence and Cisco Unified Personal Communicator licensing should first be enabled on the Cisco Unified Presence server.

D.
Do not license the same user in multiple clusters.