Binary Authorization in GKE requires attestations to validate container images before deployment. The correct approach involves creating an attestor (to vouch for images) and a policy (to enforce the requirement). After regression tests pass in the Cloud Build pipeline, an attestation for the image must be created. This ensures only attested images (with passed tests) are deployed. Option C directly addresses this by creating the attestation post-testing. Other options either focus on unrelated security measures (D), vulnerability scans (B), or introduce unnecessary components like Voucher (A), which is not part of the standard Binary Authorization workflow.