The correct answer is C.
The Declaration of Independence was signed in 1776, after the American Revolution, and stated that the Thriteen American Colonies were no longer under British rule, and would now be sovereign states.
The U.S Constitution was adopted in the same year, establishing a federal government made up of three branches: the the legislative, the executive, and the judicial.
These two displaced the monarchic system that was instated in America at that time in favour of a federal government in which citizens did not have to answer to a king, but to a representative chosen by the mayority.