Question: What triggers mobility registrations for a UE served by an MBSR cell when it observes a change of TAC and/or cell IDs?
Option 1: The UE's location area changes.
Option 2: The MBSR cell's configuration is updated by the OAM.
Option 3: The new TAC is not in the TAI list in the RA.
Option 4: The UE's connection to the MBSR is lost.
Explanation: When a UE served by an MBSR cell observes a change of TAC and/or cell IDs, it may trigger mobility registrations if the new TAC is not in the Tracking Area Identity (TAI) list in the Routing Area (RA). This ensures that the UE updates its location information with the network to maintain connectivity.