Question: What is the primary purpose of the Nnef_PFDManagement_Subscribe service operation in the 5G System?
Option 1: To provide NF consumers with a list of available PFDs for Application Identifiers.
Option 2: To allow NF consumers to modify existing PFDs for Application Identifiers.
Option 3: To enable NF consumers to subscribe to notifications of changes to PFDs for specific Application Identifiers.
Option 4: To permit NF consumers to delete existing PFDs for Application Identifiers.
Explanation: The Nnef_PFDManagement_Subscribe service operation is used by NF consumers to explicitly subscribe to notifications of changes to PFDs (Policy and Charging Control Function Data) for specific Application Identifiers. This allows the NF consumers to stay informed about updates to the PFDs, which is essential for proper policy and charging control in the 5G System.