Question: In a single-registration mode, what triggers the UE to include a specific IE when performing an inter-system change from S1 mode to N1 mode?
Option 1: When the UE has locally activated EPS bearer context(s) for which interworking to 5GS is supported.
Option 2: When the UE receives a request from the network to deactivate EPS bearer context(s).
Option 3: When the UE has locally deactivated EPS bearer context(s) for which interworking to 5GS is supported without notifying the network while in S1 mode.
Option 4: When the UE is in dual-registration mode and performs an inter-system change.
Explanation: The correct answer is Option 3 because, according to the specification, the UE includes this IE when it has locally deactivated EPS bearer context(s) for which interworking to 5GS is supported without notifying the network while in S1 mode. This scenario requires the UE to inform the network about the deactivation of EPS bearer contexts during the inter-system change from S1 mode to N1 mode.