Which of the following statements about the application of the Policy Centralization pattern is true?

A: Service agents can check for policy compliance at runtime. B: A policy framework that supports both the definition of policies and their consistent runtime enforcement is essential to meeting the goals of the Policy Centralization pattern. C: Enterprise service bus products sometimes use proprietary policy formats which can lead to vendor lock-in and incompatibilities with other enterprise service bus products. D: All of these statements are true.