Correct answer - "Versioning can be enabled only for a specific folder" : The versioning state
applies to all (never some) of the objects in that bucket. The first time you enable a bucket
for versioning, objects in it are thereafter always versioned and given a unique version ID.
"Overwriting a file increases its versions" - If you overwrite an object (file), it results in a
new object version in the bucket. You can always restore the previous version
"Deleting a file is a recoverable operation" - Correct, when you delete an object (file), Amazon
S3 inserts a delete marker, which becomes the current object version and you can restore the
previous version
"Any file that was unversioned before enabling versioning will have the 'null' version" - Objects
stored in your bucket before you set the versioning state have a version ID of null. Those
existing objects in your bucket do not change
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