The case of marbury v. madison, 1803, is a landmark case because?

Marbury v. Madison was the first case in which the judicial branch used judicial review (a power which was established in this case) to declare an act of Congress (or the federal government in general) unconstitutional. This is an extremely important precedent because it allows the Supreme Court to assure that the other branches of the government remain loyal to the Constitution.

Sorry to say i don't have the answer