You are asked to write an on-box script that will be triggered when a specific...

Aneventscript is used to automate responses to system events in Junos, such as an interface going down. These scripts are triggered automatically when a specified event occurs, making them suitable for tasks like monitoring interface status and executing actions when the status changes.

Option B (event)is correct because event scripts are designed for reacting to system events like an interface going down.

Option A (commit)is used for configuration changes,Option C (operation)is used for operational tasks, andOption D (SNMP)is not applicable in this context.

Supporting References:

Juniper Networks Event Scripts Documentation:Details how event scripts are used to automate responses to specific system events in Junos