Which Azure service provides a fully managed relational database?

Azure SQL Database is the service that provides a fully managed relational database. It is designed to handle relational data using SQL Server technology, offering features such as automatic backups, scaling, security updates, and high availability without the user needing to manage the underlying infrastructure. This fully managed environment significantly reduces the operational burden on developers, allowing them to focus more on building applications than on database maintenance.

The other options do not fulfill the requirement of a fully managed relational database. Azure Cosmos DB, while a fully managed database service, is a NoSQL database designed for high scalability and low latency but does not provide relational data capabilities. Azure Blob Storage and Azure Table Storage are both storage solutions but are used for unstructured and semi-structured data, respectively, and not specifically for relational database management. Thus, Azure SQL Database is the only choice that meets the criteria for a fully managed relational database solution within Azure.