What action must be taken with Form D's after they have been fulfilled or canceled?

Form D's serve as authorization documents within rail operations, specifically for the movement of trains or work crews under specific conditions. After these forms have been fulfilled or canceled, marking them with an 'X' and retaining them for a set period, such as seven days, provides a clear record of what has transpired. This practice is essential for operational integrity, as it allows for tracking past authorizations and ensures that any necessary audits or inquiries can be addressed efficiently.

Retaining the forms for a week allows for a brief window during which they can be reviewed if any issues arise concerning the movements that were authorized under those forms. Marking them with an 'X' signals that they are no longer active and ensures that anyone reviewing the documentation understands their status without confusion. This process supports accountability and transparency within the operational framework of railway dispatching.

The other options do not align with standard procedures for maintaining records in rail operations. For instance, destroying them immediately would eliminate critical historical data, while filing them for future reference might lead to unnecessary complications if the documents are still holding active relevance. Returning them to the dispatcher contradicts the need for local record-keeping following the completion of those movements.