Question: During TDF Session Termination, what is the primary purpose of sending accumulated usage information for all monitoring keys with a CC-Request-Type AVP set to "TERMINATION_REQUEST"?
Option 1: To initiate a new billing cycle for ongoing services.
Option 2: To request additional resources for an existing service.
Option 3: To update the subscriber's profile with new preferences.
Option 4: To report final usage statistics to the Policy and Charging Control (PCC) system.
Explanation: The correct answer is Option 4 because, according to telecom principles for session management and billing, terminating a session (in this case, a TDF session) typically involves reporting all accumulated usage to ensure accurate charging and to update the user's account status. This aligns with standard Policy and Charging Control (PCC) system functions, which rely on such reports for proper billing and resource management. The other options do not directly relate to the primary action taken during session termination in the context of telecom billing and resource management.