Option B is correct because the --splits option is specifically designed for traffic splitting between different versions of a service in App Engine. This method allows you to easily specify that 98% of users continue to see the current version while 2% are served the new version, facilitating a simple and effective testing process. Options A, C, and D are incorrect for various reasons: A and D suggest creating a new App Engine application, which is not possible as a GCP project can only have one App Engine application. Option C's --migrate option is for data migration, not traffic splitting, making it unsuitable for this scenario. For more information, refer to the App Engine documentation on traffic splitting and an overview of App Engine.