Correct option is A
The essential characteristics of the Federation in the USA are: • Supremacy of the Constitution (A): The Constitution is supreme. • Distribution of powers amongst the various organs of the federation and of regional units of the federation by the provision of the constitution (B). • Judicial review or enforcement of that supreme constitution as law (C): Judicial review ensures that the Constitution is enforced as law. The Rule of Law (D) is not strictly a defining characteristic of the USA federation.