Option A is correct because it aligns with Google's recommended best practices for managing infrastructure changes. Using Deployment Manager templates allows for a declarative description of infrastructure changes, and storing these templates in Cloud Source Repositories offers version control and collaboration benefits. Cloud Source Repositories are designed for hosting and versioning source code, making them ideal for managing Deployment Manager templates as configuration files. This approach facilitates tracking changes, managing versions, and effective team collaboration. Options B, C, and D are incorrect as they either suggest applying changes before review or storing configuration files in less suitable locations like Cloud Storage buckets or saving command outputs, which do not provide a clear description of proposed changes for review.