Question: In a 3GPP system, what is the primary purpose of the registration process in relation to charging and billing?
Option 1: To enable direct commercial transactions between the serving network operator and the user's home environment without needing trusted third parties.
Option 2: To authenticate users before they incur charges, allowing the home environment to delegate charging authority to the serving network operator.
Option 3: To facilitate optimal media routing for all subscribers across different networks.
Option 4: To establish a commercial relationship directly between the visited network and the end-user.
Explanation: The correct answer highlights the key aspect of the registration process - authenticating users to enable the delegation of charging authority. This is crucial for secure and trusted billing practices in telecom networks, ensuring that charges are accurately incurred and managed between the home environment and the serving network operator, even when they have no direct commercial dealings.