Which of the following is NOT part of the U.S. government structure?

The correct answer is D, as a Political Action Committee (PAC) is not part of the official U.S. government structure. While PACs play a significant role in the political landscape by raising and spending money to influence elections and legislation, they operate independently from the government and its branches.

The Constitution, on the other hand, is a foundational document that outlines the structure and powers of the government, detailing the framework for how the federal government operates. The Senate is a specific component of the legislative branch, responsible for making laws and representing the states at the federal level. The Executive Branch, headed by the President, is one of the three branches of government responsible for enforcing laws and managing the administration. Each of these components plays a crucial role in the functioning of the federal government, whereas PACs do not hold any official government authority or role within that structure.