The correct answer is A) separation of powers.
The idea from the Baron de Montesquieu that influenced the Founding Fathers was "the separation of powers."
Charles-Louis de Secondat, better known as Baron de Montesquieu (1689-1755) was a brilliant French thinker and philosopher that had many great political ideas. He is considered one of the brightest minds of the Enlightenment. His book "The Spirit Of Laws" that heavily influenced the American founding fathers and other revolutionary movements.
The other options of the question were B) natural law. C) social contract. D) Declaration of Independence.