To securely access Google Cloud services from within GKE, the recommended approach is to use Workload Identity (Option B). Workload Identity allows Kubernetes service accounts to impersonate Google service accounts, providing fine-grained access control without exposing static credentials. Assigning a service account to GKE nodes (Option A) grants broad permissions to all Pods on the node, violating least privilege. Storing credentials as a Secret (Option C) is insecure and outdated. GKE RBAC (Option D) manages Kubernetes resource permissions, not access to Google Cloud services.