What is the PRIMARY advantage of using a separate authentication server (e.g., Remote Access DialIn User System, Terminal Access Controller Access Control System) to authenticate dial-in users?

A.
Single user logons are easier to manage and audit.

B.
Each session has a unique (one-time) password assigned to it.

C.
Audit and access information are not kept on the access server.

D.
Call-back is very difficult to defeat.

Explanation:
TACACS integrates the authentication and authorization processes. XTACACS keeps the
authentication, authorization and accounting processes separate. TACACS+ improves XTACACS by
adding two-factor authentication. – Ed Tittle CISSP Study Guide (sybex) pg 745