Option C is correct because it adheres to the best practice of isolating development and production environments by creating a new GCP project and replicating the setup there, ensuring no network routes exist between them. Option A is incorrect as it suggests using the same project, which does not isolate the environments. Option B is incorrect because it involves using another team's production project, failing to isolate environments. Option D is incorrect as a Shared VPC allows communication between projects, violating the security requirement. For more details, refer to Google's best practices on VPC design.