Which combination of steps will enhance the security of AWS CloudFormation?

Which is not a restriction on AWS EBS Snapshots?
A. Snapshots which are shared cannot be used as a basis for other snapshots.
B. You cannot share a snapshot containing an AWS Access Key ID or AWS Secret Access Key.
C. You cannot share unencrypted snapshots.
D. Snapshot restorations are restricted to the region in which the snapshots are created.