Final answer:
The best example of Checks and Balances in the Constitution is the process outlined for passing laws in which the President can veto legislation from Congress but can be overridden by a two-thirds majority in both the House and the Senate.
Step-by-step explanation:
The statement from the Constitution that best exemplifies the principle of Checks and Balances is option a: "Every Bill which shall have passed the House of Representatives and the Senate, shall, before it becomes a Law, be presented to the President of the United States; If he approves, he shall sign it, but if not, he shall return it." This portion of the Constitution outlines the process by which the legislative branch (Congress) and the executive branch (President) check each other's power during the enactment of laws. The President has the power to veto legislation, but Congress can override this veto with a two-thirds majority vote in both the House and Senate. This is a clear example of how the framing of the Constitution provides a built-in system that ensures no single branch becomes too powerful, adhering to the Baron Montesquieu's idea of checks and balances.