The best answer is A, which is to assign global unique identifiers (GUID) to each data entry. This method ensures that each data transmission, whether original or re-transmitted, will have a unique identifier, making deduplication straightforward. While using hash values (Option D) may seem effective, it can be less efficient and error-prone because the timestamp being part of the payload can cause different hashes for essentially the same data content. By assigning a GUID, you can eliminate these issues and reliably identify duplicates.