Data at rest refers to data that is stored in a persistent state on any device or media, such as hard drives, tapes, or cloud storage. Data at rest does not move for long periods of time unless it is accessed or modified by authorized users or applications. A cold site (A) is a backup location that has minimal or no equipment and resources to resume business operations in case of a disaster. On-site retention © is a policy of keeping backup data on premises for a certain period of time before transferring it to an off-site location. Off-site storage (D) is a method of storing backup data in a remote location that is physically or logically separated from the primary site. Reference: https://docs.microsoft.com/en-us/azure/security/fundamentals/encryption-atrest https://www.techopedia.com/definition/144/cold-site https://www.enterprisestorageforum.com/backup/onsite-offsite-backup.html https://www.techopedia.com/definition/24195/offsite-storage