E. Both B and D. Option B suggests maintaining customer-managed key management and revoking or deleting keys from the key management system to prevent the data from being accessed again. By managing their own keys and ensuring the revocation or deletion of those keys, customers can effectively control access to their data and prevent unauthorized access or retrieval. Option D suggests keeping the keys stored on the client side, ensuring their security, and granting users the ability to delete their own data. By having the keys securely stored and giving users control over their data, they can actively delete their data and ensure its removal from the cloud environment. By combining both options B and D, customers can exercise strong control over their data, including the ability to revoke access through key management and allowing users to delete their own data. This approach ensures that the data is properly removed from the public cloud environment, including any associated media such as backup tapes

E. Both B and D. To ensure that all data has been removed from a public cloud environment, including all media such as back-up tapes, the best approach is to combine both options B and D. B. Maintaining customer-managed key management and revoking or deleting keys from the key management system: By managing their own encryption keys, customers can have greater control over their data. When data is no longer needed or when the customer wants to ensure its complete removal, revoking or deleting the encryption keys associated with that data can render it inaccessible. This ensures that even if the data is still stored in the cloud environment, it cannot be decrypted and accessed. D. Keep the keys stored on the client side: Storing encryption keys securely on the client side ensures that the keys are under the control of the customer. By having the ability to delete their own data using their keys, customers can actively manage and remove their data from the public cloud environment. This eliminates reliance on the cloud provider for data deletion.

Both B and D are ways to ensure the data is deleted.

I forgot to vote in my previous comment. B as D doesn't allow customer to directly delete data.

I would agree with E, but that point in answer D is problematic: storing the keys on customer side doesn't mean the customer has all permissions to delete all data from the Cloud. Of course the access of data can be prevented by the own-hosted keys, but it is not equal with the data deletion.

The best way to ensure that all data has been removed from a public cloud environment, including all media such as backup tapes, is by selecting option E: Both B and D. Option B, maintaining customer-managed key management and revoking or deleting keys from the key management system, ensures that the data cannot be accessed again by revoking the encryption keys. This prevents unauthorized access to the data even if the cloud provider still possesses the encrypted data. Option D, keeping the keys stored on the client side, provides an additional layer of security. By securely storing the encryption keys on the client side, the users have the ability to delete their own data when necessary. This gives the users more control over their data and ensures that it is properly removed from the cloud environment.