EBS Snapshots occur _____

A.
Asynchronously

B.
Synchronously

C.
Weekly

Explanation:
Snapshots occur asynchronously; the point-in-time snapshot is created immediately, but the
status of the snapshot is pending until the snapshot is complete (when all of the modified
blocks have been transferred to Amazon S3), which can take several hours for large initial
snapshots or subsequent snapshots where many blocks have changed.

http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ebs-creating-snapshot.html