Which of the following is the best example of checks and balances within the U.S. government?

a)The Chief Justice of the U.S. Supreme Court resigns.
b)The President approves a recommendation of a Cabinet member.
c)The House of Representatives fails to pass a bill introduced by the Speaker of the House.
d)A law is passed by Congress and signed by the President. It then is declared unconstitutional by the U.S. Supreme Court.