Which additional configuration should be made to fulfill the user’s request?

A user’s phone is already configured for Single Number Reach, and the user wants a feature to move an active call from a mobile phone to a desk phone and vice-versa. As an administrator, which additional configuration should be made to fulfill the user’s request?
A. Use Dialed Number Analyzer to determine if the user extension can dial the mobile phone.
B. Add the mobility key to the softkey template that the desk phone is using.
C. Check to make sure that the Resume softkey option appears on the desk phone.
D. Confirm that the desk phone is subscribed to Cisco Extension Mobility.