Minimize GKE attack surface per best practices for the EHR environment.

The correct option minimizes the GKE attack surface by ensuring both the control plane and worker nodes are isolated within a private network. A private GKE cluster with a private control plane endpoint means the Kubernetes API server is only accessible from within the VPC network, significantly reducing exposure to the public internet. Enabling Master Authorized Networks further restricts access to the control plane to specified CIDR blocks, adding another layer of security. Using a public GKE cluster (options 2 and 4) inherently exposes the cluster to the internet, increasing the attack surface even with firewall rules. While a private GKE cluster with a public control plane endpoint (option 3) hides the worker nodes, the control plane remains publicly accessible, which is less secure than a fully private setup.