The answer is number a is true
Federalism limits the power of government in the United States through the creation of two sovereign powers: the national government and state governments. In this way, it regulates the influence these have. Separation of powers establishes internal limits; it divides government against itself, giving separate functions to different branches and compelling them to share power, so neither of them becomes predominant.
By separating powers, these are split among the executive (president, vice president, Cabinet), legislative (Congress, House of Representatives and Senate), and judicial branches (Supreme Court and other courts), which are definite departments of American national government.
