Final answer:
The correct command to filter SYSLOG messages by severity level on Cisco devices is 'logging console [severity level]', with the severity level being a numerical value from 0 for emergencies to 7 for debugging.
Step-by-step explanation:
The command that allows you to filter SYSLOG messages by severity level is most commonly found in Cisco network devices, and the correct syntax among the provided options is:
logging console [severity level]
To use this command, replace '[severity level]' with the desired level you wish to set; for example, if you want to see only warnings and more severe messages, you would use:
logging console 4
In this context, '4' represents the severity level for warnings. The levels are numbered from 0 (emergencies) to 7 (debugging), with a lower number indicating a more severe condition.