Final answer:
The phrase 'sent to' completes the sentence properly, using the past participle 'sent' after 'have them', and the preposition 'to' for direction.
Step-by-step explanation:
The correct phrase to complete the sentence "Once the files are ready, please have them .........me" is "D. sent to". This option correctly uses the past participle 'sent', which is required after 'have' when indicating a completed action by someone else, and the preposition 'to' to indicate the direction toward the person who will receive the files.