With RADIUS down, which configuration secures the console port using a local user and local authentication?

The correct configuration establishes a local username and password, then applies local authentication to the console line. username localuser secret plaintextpassword creates the local user. line con 0 enters console line configuration mode. login authentication default instructs the console line to use the default authentication method, which, without AAA configured for login, defaults to local authentication. privilege level 15 grants full administrative access upon successful login. The first option is incorrect because aaa new-model enables AAA, which would then require a specific AAA method for authentication, not just a simple password command on the line. The second option is incorrect because it configures RADIUS as the primary authentication method, which would fail if RADIUS is down. It also incorrectly mixes aaa authorization with aaa authentication login default radius. The third option is incorrect because no login local disables local authentication, leaving the console unsecured or relying on other methods not specified.