A. Stop the DB instance and modify it to enable encryption. Apply this setting immediately without waiting for the next scheduled RDS maintenance window.
B. Stop the DB instance and create an encrypted snapshot. Restore the encrypted snapshot to a new encrypted DB instance. Delete the original DB instance, and update the applications to point to the new encrypted DB instance.
C. Stop the DB instance and create a snapshot. Copy the snapshot into another encrypted snapshot. Restore the encrypted snapshot to a new encrypted DB instance. Delete the original DB instance, and update the applications to point to the new encrypted DB instance.
D. Create an encrypted read replica of the DB instance. Promote the read replica to master. Delete the original DB instance, and update the applications to point to the new encrypted DB instance.