Answer: A. US Constitution
Expiation: Clause 2 of Article VI of the U.S Constitution, known as the Supremacy Clause, establishes the U.S. Constitution and "and all treaties made, or which shall be made" as the Supreme Law of the Land, therefore, all states, federal officers and judges are bound by the Constitution, meaning that in case of a conflict between state and federal laws, the federal laws is the one that shall prevail.
