Final answer:
The command that allows you to filter SYSLOG messages by severity-level is 'set syslog severity-level'. This command is used to specify the level of severity for SYSLOG messages.
Step-by-step explanation:
The command that allows you to filter SYSLOG messages by severity-level is c) set syslog severity-level.
This command is used in computer systems and networking to specify the level of severity for SYSLOG messages. SYSLOG is responsible for collecting and transmitting messages from various system components.
By using this command, you can set the desired level of severity for SYSLOG messages, helping you identify and prioritize critical system events.