Based on the excerpt, James Madison believed that federalism is needed in government because it limits governmental authority in order to avoid abuse of power. This is reflected in the way he describes the division of power among different governments and departments, which creates checks and balances.
For the second question, the statement that best represents the role of the judicial branch of government is "The judicial branch has the ability to declare a law unconstitutional." This power is a key function of the judicial branch, ensuring that laws align with the Constitution.