Which AWS service meets this requirement?

Explanations:

AWS CloudFormation is a service specifically designed to manage infrastructure as code. It allows users to define and provision AWS resources using a declarative template format, making it ideal for automating and version-controlling cloud infrastructure.

AWS Elastic Beanstalk is a platform-as-a-service (PaaS) that simplifies the deployment and management of applications. While it manages the underlying infrastructure, it does not directly enable users to manage that infrastructure as code.

AWS Cloud9 is an integrated development environment (IDE) that allows developers to write, run, and debug code in the cloud. It does not focus on managing infrastructure as code but rather provides tools for coding and collaboration.

AWS CloudShell is a browser-based shell that provides command-line access to AWS services. While it can be used to execute scripts and commands, it does not serve as a service for managing infrastructure as code like AWS CloudFormation does.