The primary goal of whole business continuity and disaster recovery exercise should be health and human safety.

The risk-management process has four components
1. Framing risk
2. Assessing risk
3. Responding to risk
4. Monitoring risk

File-level encryption: Database servers typically reside on volume storage. For this deployment, you are encrypting the volume or folder of the database, with the encryption engine and keys residing on the instances attached to the volume.
External file system encryption protects from media theft, lost backups, and external attack but does not protect against attacks with access to the application layer, the instances 0S, or the data

All the options given are correct methods of destroying data but when it comes to data in cloud. the most suitable method is cryptographic erasure.
Definition: Cryptographic Erasure
Cryptographic erasure is the process of using encryption software (either built-in or deployed) on the entire data storage device. and erasing the key used to decrypt the data.

Storing is the act committing the digital data to some sort of storage repository and typically occurs nearly simultaneously with creation.
Reference: CSA Security Guidelines V.4(reproduced here for the educational purpose)