Which AAA command validates users against the local router database to authorize execution of configuration (exec) commands?

The aaa authorization exec default local command is correct because it specifically configures authorization for EXEC (command-line) access using the local router database. Authorization determines what a user is allowed to do after they have been authenticated. The exec keyword specifies that this rule applies to EXEC shell access. The default keyword applies this method to all users not explicitly covered by other authorization methods, and local specifies the local database as the authorization source. aaa authentication network default local and aaa authentication exec default local are incorrect because they deal with authentication (verifying identity), not authorization (determining permissions). aaa authorization network default local is incorrect because network authorization applies to network services like PPP or 802.1X, not EXEC commands.