Automatic backup retention of a DB system is disabled.

When automatic backup retention of a DB system is disabled,deleting the DB system(Answer C) will delete all automatic backups of the DB system.

Automatic Backups: These are backups created automatically by the OCI service to ensure data protection.

Backup Deletion: If automatic backups are disabled and you delete the DB system, all associated automatic backups are also deleted. This operation is irreversible, and you should ensure that necessary backups are taken before deleting the DB system.

References:

OCI MySQL Database Service Backup and Restore