What principle of the constitution is clearly demonstrated in the process of a bill becoming a law

Checks and Balances: Every branch needs the consent of at least one other branch so they can make a major decision. All branches have equal power.

Explanation:

The Checks and Balances principle is demonstrated in the process of a bill becoming a law because The Constitution states that for any bill to become a Law it must be approved by the House of Representatives, the Senate and the President. Every bill passes by the House of Representatives and the Senate. Afterwards the President reviews the law in order to approve it and sign it, when he doesn't approves it he sends back his observations and objections to the House where the bill was originated. If two thirds of that House agree to pass the law then it is passed to the other House in order for them to review the objections the President made, if two thirds of this other House votes in favor then it shall become a Law.