Which AWS service is designed for building, training, and deploying machine learning models at scale?

Correct answer: Amazon SageMaker

Option A is correct because Amazon SageMaker is AWS's fully managed platform specifically designed to cover the entire machine learning lifecycle, including building, training, tuning, and deploying ML models at scale with built-in algorithms, notebooks, and model hosting. Option B is incorrect because AWS Lambda is a serverless compute service for running event-driven code functions, and while it can invoke ML endpoints, it does not provide ML training or model management capabilities. Option C is incorrect because AWS CloudFormation is an infrastructure-as-code service for provisioning and managing AWS resources through templates, not an ML development platform. Option D is incorrect because Amazon EC2 provides virtual machine compute capacity and can be used as raw infrastructure for ML workloads, but it offers no managed ML tooling, automated training pipelines, or model deployment services.