The US Constitution is referred to as the “supreme law of the land.” Option A is correct
The United States Constitution is The Supreme Law of the United States.
The Supremacy Clause in the Constitution states:
“This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land; and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding.”
The key point of the Doctrine was to separate the influence in which The United States and European powers would have. Europe would have no intervention within the Western Hemisphere and likewise the United States would not become entangled in European affairs.