Final answer:
The correct option is a.The Constitution prevents the national government from becoming too powerful through the Separation of Powers, dividing responsibilities among three branches that check and balance each other.
Step-by-step explanation:
The part of the Constitution that keeps the national government from becoming too powerful is separation of Powers. The Founding Fathers established a national government divided into three branches: legislative, executive, and judicial.
Each branch has its own responsibilities and powers, but they are designed to check and balance each other and thus require cooperation to function. This system ensures that no single branch becomes too dominant, protecting citizens' rights by preventing the concentration of power.