Refer to the below.

Which statement about this debug output is true?

A.
The requesting authentication request came from username GETUSER.

B.
The TACACS+ authentication request came from a valid user.

C.
The TACACS+ authentication request passed, but for some reason the user’s connection was
closed immediately.

D.
The initiating connection request was being spoofed by a different source address.

Explanation:
http://www.cisco.com/en/US/docs/ios/12_2/debug/command/reference/dbfser.html
debug tacacs
To display information associated with the TACACS, use the debug tacacs privileged EXEC
command. The no form of this command disables debugging output.
debug tacacs
no debug tacacs
The following is sample output from the debug tacacs command for a TACACS login attempt that
was successful, as indicated by the status PASS:
Router# debug tacacs
14:00:09: TAC+: Opening TCP/IP connection to 192.168.60.15 using source 10.116.0.79
14:00:09: TAC+: Sending TCP/IP packet number 383258052-1 to 192.168.60.15
(AUTHEN/START)
14:00:09: TAC+: Receiving TCP/IP packet number 383258052-2 from 192.168.60.15
14:00:09: TAC+ (383258052): received authen response status = GETUSER
14:00:10: TAC+: send AUTHEN/CONT packet
14:00:10: TAC+: Sending TCP/IP packet number 383258052-3 to 192.168.60.15
(AUTHEN/CONT)
14:00:10: TAC+: Receiving TCP/IP packet number 383258052-4 from 192.168.60.15
14:00:10: TAC+ (383258052): received authen response status = GETPASS
14:00:14: TAC+: send AUTHEN/CONT packet
14:00:14: TAC+: Sending TCP/IP packet number 383258052-5 to 192.168.60.15
(AUTHEN/CONT)
14:00:14: TAC+: Receiving TCP/IP packet number 383258052-6 from 192.168.60.15
14:00:14: TAC+ (383258052): received authen response status = PASS
14:00:14: TAC+: Closing TCP/IP connection to 192.168.60.15