A developer creates a Dispatcher which extracts information from the top 30 mail messages in Microsoft Outlook and uploa

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A developer creates a Dispatcher which extracts information from the top 30 mail messages in Microsoft Outlook and uploads that information into a queue.
What is the recommended way to avoid processing duplicates of the same Queue Items?

A. Create an Excel file of processed Queue Items and loop through the list to check if the current Queue Item has been processed before.
B. Add a descriptive "Reference" in the "Add Queue Item" activity and check that it does not equal the "Reference" of the Queue Item last processed.
C. Set the "Unique Reference" of the queue to "Yes" and "Auto Retry" of the queue to "No".
D. Set the "Unique Reference" of the queue to "Yes" and add a descriptive "Reference" in the "Add Queue Item" activity.