Choose all that are required for deduplication to identify two duplicates files.

To identify duplicate files during deduplication, it is crucial to utilize a method that can effectively differentiate one file from another based on its content. Utilizing an MD5 hash combined with the subject line is a method used in some deduplication strategies, but it may not be comprehensive enough for all scenarios since the subject line could change while the file content remains the same.

The combination of recipient and message body hash, on the other hand, provides a robust approach. The recipient identifies to whom the files were sent, while the message body hash captures the unique content of the file. If both the recipient and the hash of the file content match, it strongly indicates that the files are duplicates. This two-pronged approach minimizes the risk of erroneously marking files as duplicates based solely on less distinctive attributes like size or file type.

Other pairs like recipient and size or attachment and file type are less effective for deduplication purposes. Size alone is not adequate because different files can have the same size but be entirely different, while attachment and file type also don’t guarantee content similarity. Thus, the criteria of recipient and message body hash is the most effective and comprehensive for identifying duplicate files.