Final answer:
To allow automatic closure of incident tasks once the incident is closed, one should adjust the relevant setting in the IT Service Management system, such as enabling a property that governs task closure behavior.
Step-by-step explanation:
The question relates to configuring an IT Service Management system to allow automatic closure of related incident tasks once the primary incident is closed. The correct way to enable this function depends on the specific software application's configuration settings. Assuming the software allows for such configurations, one could look for a setting similar to 'Set property .incident.incident_task.closure to true' or 'Set property .incident.incident_task.closure to auto', which would determine the behavior of task closures related to an incident.
However, options A and B seem incorrectly formatted and don't reflect standard property naming conventions. Also, certain IT Service Management systems might require additional scripting or workflow adjustments to ensure that the closure of an incident cascades to its related tasks automatically. It's important to consult the official documentation of the specific ITSM software you are using for the correct procedure.