The core requirement is to ensure only scanned and verified containers can run in the environment, which is a deployment-time enforcement action.

Binary Authorization is the service designed for this purpose. It is a deployment-time security control that ensures only trusted container images are deployed on Google Kubernetes Engine (GKE) or other supported container platforms. The core mechanism it uses to verify that an image has completed required steps (like a vulnerability scan) is an attestation.

Extracts:

"GCP Binary Authorization is a security feature designed to prevent the deployment of unverified, unauthorized, or potentially malicious container images to Kubernetes clusters." (Source 1.1)

"Binary Authorization ensures that only images that are signed by trusted entities (such as a trusted attestation authority) are allowed to be deployed." (Source 1.1)

"Binary Authorization aims to reduce the risk of deploying defective, vulnerable, or unauthorized software in this type of environment. Using this service, you can prevent images from being deployed unless it satisfies a policy you define." (Source 1.2)

"The most common Binary Authorization use cases involve attestations. An attestation certifies that a specific image has completed a previous stage... Attestations signify that the associated image was built by successfully executing a specific, required process. For example, the attestation might indicate that the image has passed all required end-to-end functional testing in a staging environment." (Source 1.2, 1.4)

"After a container image is built, an attestation can be created to affirm that a required activity was performed on the image such as a regression test, vulnerability scan, or other test." (Source 1.5)

Option A correctly identifies the two necessary components for this deployment-time enforcement: Binary Authorization for policy enforcement and attestations to certify that the vulnerability scan (or other required check) has been completed and verified.