The correct answer is check and balances, federalism, and separation of powers.
The US Constitution is the basis for our current government in the United States. All of the aforementioned elements are part of this government.
1) Checks and balances- Each branch of the federal government (judicial, legislative, and executive) have the power to keep each other in line. For example, the executive branch can veto laws passed by the legislative branch.
2) Federalism- This refers to the idea that there are multiple forms of government within a country. In this US, we have federal, state, and local governments.
3) Separation of powers- Each branch of the federal government has different responsibilities. For example, the judicial branch is responsible for interpreting what the laws mean.