Question: Upon receiving a reset indication from the VLR, what action may the MME take when a UE (User Equipment) still attached for non-EPS services sends a combined tracking area update request?
Option 1: The MME will always perform a network-initiated detach with detach type "IMSI detach" immediately.
Option 2: The MME will ignore the request until the VLR-Reliable flag is set to "true".
Option 3: The MME may perform a location update for EPS (Evolved Packet System) services only.
Option 4: The MME may perform immediately the location update for non-EPS services procedure.
Explanation: According to the specifications, when the VLR-Reliable flag is set to "false" (indicating a reset indication from the VLR), and upon receiving a combined tracking area update request from a UE still attached for non-EPS services, one of the actions the MME may take is to perform immediately the location update for non-EPS services procedure. This ensures continuity of service for the UE on non-EPS services despite the reset indication from the VLR.