Answer:
C, Separation of Powers
Step-by-step explanation:
Answers A and D can be ruled out of the question, as executive orders and federalism are not about the overall order of the central government, so it's between answers B and C.
Checks and balances is put into place to ensure that one branch of government does not have more power than another, while seperation of powers is put into place to make sure that each branch of government has its own specific duties and responsibilities. This makes separation of powers the correct answer.