Final answer:
Both RADIUS and TACACS+ provide combined authentication and authorization services, which makes option C) Both A and B, the correct answer.
Step-by-step explanation:
The question asks for a service that combines authentication and authorization services into a single function. RADIUS (Remote Authentication Dial-In User Service) and TACACS+ (Terminal Access Controller Access-Control System Plus) both provide these services, so the correct answer is C) Both A and B. RADIUS is a networking protocol that provides centralized Authentication, Authorization, and Accounting (AAA) management for users who connect and use a network service.
Whereas TACACS+ is a protocol that provides remote access authentication and related services, like RADIUS, it separates the authentication process from the authorization and accounting processes, providing more control over these elements.