Question: What action can a User Equipment (UE) take if it receives a CS SERVICE NOTIFICATION message or a paging indication with the CN domain indicator set to "CS" after requesting "SMS only" in the combined attach procedure or combined tracking area updating procedure?
Option 1: The UE must respond to the CS SERVICE NOTIFICATION message or the paging indication.
Option 2: The UE can ignore the CS SERVICE NOTIFICATION message but must respond to the paging indication.
Option 3: The UE may ignore both the CS SERVICE NOTIFICATION message and the paging indication with the CN domain indicator set to "CS".
Option 4: The UE must reject the CS SERVICE NOTIFICATION message or the paging indication.
Explanation: According to the specified behavior, a User Equipment (UE) that has requested "SMS only" in certain procedures can choose to ignore specific messages related to Circuit Switched (CS) services. This allows the UE to focus on SMS-related communications while disregarding other CS service notifications or paging indications with the CN domain indicator set to "CS".