Which statement about S3 multipart upload is correct?

The correct statement is that unfinished parts stay stored and billed, so you add a lifecycle rule to abort incomplete uploads. Uploaded parts stay in S3 and cost money until you complete or abort the upload.

"S3 deletes the parts of an incomplete upload automatically after 24 hours" is wrong. S3 does not clean them up on its own. This is why the lifecycle rule exists.

"If one part fails, the whole upload must restart from the first part" is wrong. Multipart upload sends parts separately and in parallel, so you retry only the failed part.

"Multipart upload is only allowed for objects larger than 5 TB" is wrong. You can use it for objects of any size above 5 MB. It is required for objects over 5 GB, because one single upload can send at most 5 GB. The maximum object size was 5 TB. AWS raised it to 50 TB in December 2025.