Explanation a backup strategy is a plan that defines how to protect data from loss or corruption by creating and storing copies of data on a different medium or location1. A backup strategy should consider the security and reliability of the backup data and the backup storage234. Based on these definitions, the best option that is a cost-effective approach to address the security and reliability concerns regarding the on-site backup strategy would be D. Migrate to a cloud backup solution24. A cloud backup solution can provide several benefits, such as: Enhanced physical security of the backup data by storing it in a remote location that is protected by multiple layers of security measures. Enhanced durability of the backup data by storing it on highly reliable storage devices that are replicated across multiple availability zones or regions. Reduced costs of backup storage by paying only for the amount of data stored and transferred, and by using features such as compression, deduplication, encryption, and lifecycle management. Increased flexibility and scalability of backup storage by choosing from various storage classes and tiers that match the performance and availability requirements of the backup data.