In response to Access-request from a client such as a Network Access Server (NAS), which of the following is not one of the response from a RADIUS Server? 

Answer options:

A. Access-Accept
B. Access-Reject
C. Access-Granted
D. Access-Challenge

C

In response to an access-request from a client, a RADIUS server returns one of three authentication responses: access-accept, access-reject, or access- challenge, the latter being a request for additional authentication information such as a one-time password from a token or a callback identifier. Source: TIPTON, Harold
F. & KRAUSE, MICKI, Information Security Management Handbook, 4th Edition, Volume 2, 2001, CRC Press, NY, page 36.