Which AWS service will automatically create and manage versions of ML models as new model artifacts are produced?

Amazon SageMaker Model Registry is the correct answer because it is specifically designed to manage the lifecycle of ML models, including versioning. It allows you to catalog models, track their versions, approve or reject them for deployment, and manage their metadata. This ensures a clear audit trail and easy rollback capabilities. Amazon ECR is a container registry for Docker images, not ML model artifacts themselves, although model images might be stored there. Model packages from Amazon SageMaker Marketplace are pre-trained models or algorithms offered by third parties, not a service for managing your own model versions. Amazon SageMaker ML Lineage Tracking records the steps and artifacts involved in an ML workflow, providing an audit trail of how a model was created, but it doesn't manage model versions in the same way the Model Registry does.