Question: What is the primary reason for including the "Allowed SSC Mode" Information Element (IE) in a response from the network?
Option 1: To indicate support for multiple SSC modes.
Option 2: To reject a PDU Session Establishment Request due to an unsupported SSC mode.
Option 3: To request additional information about the UE's capabilities.
Option 4: To confirm the successful establishment of a PDU session.
Explanation: The "Allowed SSC Mode" IE is included in a response from the network when it rejects a PDU Session Establishment Request with cause #68, indicating that the requested SSC mode is not supported. This allows the UE to understand why its request was rejected and potentially retry with a different SSC mode.