You are developing a monitoring application that runs on a Google Kubernetes Engine (GKE) cluster.

The correct answer is D because Workload Identity Federation for GKE is the recommended way to let Kubernetes workloads access Google Cloud services without service account keys. It maps Kubernetes service accounts to Google service accounts and allows workloads to receive short-lived credentials automatically. This satisfies the security policy that prohibits key creation and avoids the operational risk of storing long-lived credentials inside containers, Secrets, or images. Personal user credentials are inappropriate for production workloads because they are tied to an individual and are difficult to audit and rotate. Creating keys in another project or overriding organization policy defeats the security requirement. Workload Identity Federation provides secure, auditable, keyless authentication for GKE workloads.