Question: What is the purpose of including the "PDU Session Reactivation Result Error Cause" Information Element (IE) in a message?
Option 1: To indicate successful re-establishment of user-plane resources for all PDU sessions.
Option 2: To indicate the cause of failure to re-establish user-plane resources for one or more PDU sessions.
Option 3: To request reactivation of a specific PDU session.
Option 4: To notify the UE about an ongoing PDU session modification procedure.
Explanation: The "PDU Session Reactivation Result Error Cause" IE is included to provide information about why user-plane resources could not be re-established for one or more PDU sessions during a PDU session reactivation procedure. This allows the receiver to understand the reason behind the failure and take appropriate actions.