In multi-cluster Kubernetes environments, the challenge lies in consistently deploying interdependent applications across clusters while ensuring reliability and repeatability. The Cloud Native Platform Engineering guidance stresses the importance of a declarative approach to define applications as code, which enables teams to describe the entire application system—including dependencies, configuration, and policies—in a single manifest. This ensures that applications are treated as a cohesive unit rather than isolated workloads.

Option A is correct because declarative application deployment definitions (often managed through GitOps practices) allow for consistent and automated reconciliation of desired state versus actual state across multiple clusters. This approach supports scalability, disaster recovery, and compliance by ensuring identical deployments across environments.

Option B (separate repos per application) increases fragmentation and does not inherently manage interdependencies. Option C (direct deployments from CI/CD) bypasses the GitOps model, which reduces auditability and consistency. Option D (Helm with manual deployments) partially addresses packaging but lacks the automation and governance needed in a multi-cluster setup.