正解:C
To filter out DOT1X messages from being sent to a Syslog server, you need to apply a logging discriminator on the Cisco device. The logging discriminator will specify which messages should be excluded based on specified criteria. In this case, the criterion is to exclude messages that match the DOT1X format. The correct configuration involves creating a logging discriminator that matches the DOT1X message pattern and then applying it to the logging configuration that points to the Syslog server 10.15.20.33.