Which of the following is the cheapest storage option available in Azure?

Blob Storage is considered the most cost-effective option for storing unstructured data in Azure. It is designed to handle large amounts of unstructured data, such as images, videos, and backups, making it versatile for various applications. Blob Storage offers different access tiers—hot, cool, and archive—that allow users to optimize costs based on how frequently the data is accessed.

In contrast, File Storage is typically used for shared file storage and is likely to be more expensive owing to its additional features for file sharing and access protocols. Disk Storage is geared towards providing high-performance storage for virtual machines and other applications, and usually, incurs higher costs due to its performance capabilities. Queue Storage is designed for managing message queues and is focused on the messaging aspect rather than bulk storage, which places it in a different category that may not be purely cost-driven.

These considerations position Blob Storage as the most economical choice when considering diverse storage options within Azure's offerings.