Which AWS service provides a managed relational database?

Correct answer: Amazon RDS

Option D is correct because Amazon RDS (Relational Database Service) is AWS's fully managed relational database service, supporting engines such as MySQL, PostgreSQL, MariaDB, Oracle, and SQL Server, handling patching, backups, and replication automatically. Option A is incorrect because AWS Lambda is a serverless compute service that runs code in response to events and is not a database service. Option B is incorrect because Amazon EC2 provides virtual machine instances for general-purpose compute, and while you can install a database on EC2, the service itself is not a managed database offering. Option C is incorrect because Amazon S3 is an object storage service used for storing files and unstructured data, not a relational database.