What does a difference in md5 hash digest signify?

The choice indicating that a difference in MD5 hash digest signifies that the file is corrupt is based on a misunderstanding of what MD5 hashes represent. An MD5 hash is a cryptographic representation of a file's contents. When a file is created or altered, its MD5 hash value changes. This change occurs because even the slightest modification in the data results in a completely different hash output.

Therefore, when comparing two files, if their MD5 hash digests differ, it clearly indicates that the contents of the files are not the same, which often suggests that the file has been modified. This difference can occur due to intentional changes, such as editing the file, or accidental changes, such as corruption during storage or transmission.

On the other hand, the other options focus on different interpretations of what a differing hash might mean. A file being corrupt often implies damage that may lead to it being unreadable or losing data integrity, but the core reason for the differing hashes is primarily related to modifications rather than corruption specifically. Thus, the recognition that a differing MD5 digest is a clear indicator of changes to the file's content supports why the accurate interpretation is that the file has been modified.