The question requires a deployment strategy that ensures zero downtime, automated testing, pre-rollout testing, and quick rollback. Spinnaker is a dedicated CD tool that supports advanced deployment strategies. Option B (canary test) fits best because Spinnaker's canary deployment automates gradual rollout to a subset of users, runs automated tests, and only proceeds to full deployment if tests pass. If issues arise, it enables quick rollback. Canary testing inherently supports zero downtime by keeping the old version active during testing. Options C and D rely on kubectl, which would require manual scripting for canary/shadow testing and lack built-in automation for rollback. A/B testing (Option A) focuses on comparing versions rather than incremental, automated rollout based on test results, making it less suitable.