Question: In 5G System Network Exposure Function (NEF) Northbound interface, what protocol is utilized for authorizing access to NEF Northbound APIs, based on local configuration, using the 'Client Credentials' grant type?
Option 1: Basic Authentication Protocol
Option 2: OAuth2 Protocol (as specified in IETF RFC 6749)
Option 3: Digest Access Authentication
Option 4: Certificate-Based Authentication
Explanation: OAuth2 Protocol, specifically with the 'Client Credentials' authorization grant, is mandated for securing access to NEF Northbound APIs. This ensures that clients must first obtain a token from an authorization server before consuming services offered by the NEF, thus maintaining the security and integrity of the 5G system's network exposure.