Question: What happens to an Emergency Registered UE's RM state in the AMF after the mobile reachable timer expires?
Option 1: The UE remains in the RM-REGISTERED state.
Option 2: The UE enters the CM-IDLE state.
Option 3: The AMF may change the UE RM state for 3GPP Access to RM-DEREGISTERED.
Option 4: The UE initiates a Periodic Registration Update procedure.
Explanation: According to the reachability management rules, after the mobile reachable timer expires, the AMF may change the Emergency Registered UE's RM state for 3GPP Access in the AMF to RM-DEREGISTERED. This is done to ensure that the UE remains registered for emergency services even when it is not actively connected to the network.