Question: Under what condition is a new 'List of Service Data Volumes' container activated for WLAN-CDR charging information collection in a PDG (Packet Data Gateway) for a UE (User Equipment)?
Option 1: When the total data volume across all service data flows reaches a predefined threshold.
Option 2: Upon detection of traffic for a previously undefined bearer.
Option 3: When traffic for a defined service data flow or a new rating group is detected.
Option 4: At the expiration of a predetermined time interval since the last container was closed.
Explanation: This option correctly identifies the trigger for activating a new 'List of Service Data Volumes' container, which is the detection of traffic for either a defined service data flow or a new rating group. This aligns with the efficient management of charging information, allowing for separate counting per service data flow or rating group as specified in the WLAN-CDR charging mechanism.