Which AWS service provides a fully managed, serverless compute platform that runs code in response to events?

Correct answer: AWS Lambda

Option D is correct because AWS Lambda is the fully managed, serverless compute service that executes code in response to triggers such as API Gateway requests, S3 events, DynamoDB streams, or SNS messages, with no server provisioning required and automatic scaling to zero when idle. Option A, Elastic Beanstalk, is a platform-as-a-service that provisions and manages EC2 instances, load balancers, and other infrastructure, making it neither serverless nor event-driven in the Lambda sense. Option B, Amazon EC2, provides virtual machine instances that require the user to provision, configure, and manage the underlying server, the opposite of serverless. Option C, Amazon ECS, is a container orchestration service that runs Docker containers and, while it supports Fargate for serverless container execution, it is not the primary event-driven serverless compute platform described in the question.