An administrator must enable Telnet access to Router X using the router username and password database for authentication. Which configuration should be applied?

`line aux 0` configures the auxiliary port, which is used for out-of-band management via a modem or console, not for standard Telnet access.

`aaa new-model` enables the AAA (Authentication, Authorization, and Accounting) subsystem, which is a prerequisite for more advanced authentication schemes but is not the specific command to enable Telnet access or configure VTY lines.

This option is identical to choice D, indicating it refers to the same correct command for configuring virtual terminal lines for Telnet access.

The `line vty 0 4` command enters the virtual terminal line configuration mode, which is the necessary step to enable and configure Telnet access, including setting up local authentication using the router's username and password database, for remote users.