正解:C
The correct configuration for enabling TACACS^ authentication for remote users involves specifying the TACACS^ server details, including the IP address and the secret key, and applying the TACACS^ server group to the line configuration. Option C shows the correct configuration where the tacacs-server host command is used to define the TACACS^ server with its IP address and the key keyword to specify the shared secret. The aaa group server tacacs+ command is used to create a server group, and the server-private command within the group specifies the IP address of the TACACS^ server and the key.
Finally, the line vty configuration applies the server group to the VTY lines, which allows remote users to be authenticated via TACACS^.