How should a consultant provide access to FSL mobile app?

some technicians report that they are unable to login to the field service lightning mobile app. The Consultant confirmed that the technician has field service lightning resource license and field service lightning resource permission assign to them

How should a consultant provide access to FSL mobile app?
A . Assign a permission set
B . Modify the user profile
C . Update the public group membership
D . Modify the user record

Answer: A