B. Because all other laws in the United States must follow the rules laid out in the Constitution.
The Constitution is referred to as the "highest law in the land" because it establishes the framework for the government and serves as the ultimate legal authority. All other laws, whether they are state or federal, must comply with the Constitution; if they do not, they can be declared unconstitutional and therefore invalid. This principle is known as judicial review and is fundamental to the rule of law in the United States.