Question: In a 5G network, when does the Network Exposure Function (NEF) increment the subcounter for failed background data transfer policy applications by 1?
Option 1: Upon successful transmission of an Nnef_ApplyPolicy_Create response message to the Application Function (AF)
Option 2: When the AF requests a new background data transfer policy application
Option 3: During each packet switched traffic session establishment
Option 4: Upon receiving a policy update from the Policy Control Function (PCF)
Explanation: The NEF increments the subcounter for failed background data transfer policy applications by 1 upon transmission of an Nnef_ApplyPolicy_Create response message to AF indicating a failed application. This implies the increment happens when the NEF notifies the AF of a failure, making Option 1 correct.