You're designing a CI/CD pipeline in Google Cloud that requires ephemeral environments for testing each build. What approach would be best for dynamically provisioning and de-provisioning these environments?

*Explanation:* Option A is incorrect as managed instance groups are not ideal for ephemeral environments. Option B focuses on data orchestration rather than environment provisioning. Option D is not suitable because Cloud Functions are serverless and not meant for infrastructure provisioning. Option E does not address the dynamic provisioning and de-provisioning of environments. Option C is the correct choice, as GKE with namespaces allows you to create isolated, ephemeral environments for testing purposes.