How many IP extensions and how many terminals do I need to register for this situation?

Avaya Communicator for Microsoft Lync is registered as a H.323/SIP softphone to Communication Manager/Session Manager and can share extensions with H.323/SIP phones.

How many IP extensions and how many terminals do I need to register for this situation?
A . Register 1 extension and require 1 terminal license
B . Register 1 extension and require 2 terminal licenses
C . Register 2 extensions and require 1 terminal license
D . Register 2 extensions and require 2 terminal licenses

Answer: C