Final answer:
The "experiment" Washington mentions in the context refers to C) the democratic form of government established by the United States Constitution.
Step-by-step explanation:
From the context given, the "experiment" Washington mentions in the first paragraph refers to the democratic form of government established by the United States Constitution.
George Washington refers to the experiment in democracy, where America tried out a new form of government that included principles such as power coming from the people, limited government power, and protection of individual liberties.
This experiment in democracy was about establishing a democratic government that could serve as a worthy example of justice and benevolence for the rest of the world.