D. Modify the export job header to specify Sforce-Enable-PKChunking (Option D): When dealing with large datasets, enabling PK chunking can be beneficial. This feature allows Salesforce to break down large queries into smaller chunks based on primary keys, reducing the likelihood of time-out failures.

Options A (Modify the export query that includes standard index fields(s)) and B (Modify the export query with LIMIT clause with Batch size 10,000) are more focused on adjusting the query itself, but they might not address the specific timeout issue related to large datasets.

Option C (Modify the export job header to specify Export-in-Parallel) is not a standard Salesforce parameter, and it’s not clear how it would address the timeout issue.