Question: In which mode does the UE include the UE radio capability ID information element, and under what condition?
Option 1: NB-S1 mode, when the UE initiates a connection
Option 2: WB-S1 mode, when the UE receives a SECURITY MODE COMMAND message with the UE radio capability ID request
Option 3: MBMS mode, when the UE is in idle state
Option 4: WB-S1 mode, when the UE radio capability ID was requested within the corresponding SECURITY MODE COMMAND message
Explanation: The correct answer is Option 4 because the paragraph explicitly states that the UE includes the UE radio capability ID information element in WB-S1 mode if the UE radio capability ID was requested within the corresponding SECURITY MODE COMMAND message. This highlights the importance of the UE radio capability ID in WB-S1 mode for security purposes, such as authentication and authorization.