Cloud Run is the correct choice because it is a fully managed serverless platform that is built on Knative, which the application is already using on-premises. This ensures compatibility with the existing deployment strategy without requiring changes. Compute Engine (B) involves managing VMs, which isn't fully managed. Google Kubernetes Engine (C) requires managing Kubernetes clusters and Knative components, making it less 'fully managed' than Cloud Run. App Engine flexible environment (D) uses a different deployment model and does not natively support Knative, necessitating adjustments to the deployment process.