Final answer:
Marbury v. Madison is significant as it established the power of judicial review for the Supreme Court, empowering the judiciary to act as a check on the other branches of government.
Step-by-step explanation:
Marbury v. Madison is significant today because it established the principle of judicial review, which is the power of the courts to declare laws unconstitutional and thereby null and void. This power is crucial as it enables the judiciary to act as a check on the legislative and executive branches of the government. The correct answer to the student's question is c. It established the Supreme Court as a check against Congress. The case determined that the Supreme Court could declare an act of Congress unconstitutional, which in turn legitimized the court's authority to review and potentially nullify actions taken by the other branches of government. This case, decided by Chief Justice John Marshall in 1803, has become a cornerstone of the U.S. legal system.