The supremacy clause is within the Article four of the US constitution. It dictates the federal law to be the law of the land. It means that all the judges of the states must follow the constitution, laws and treaties of the federal government. The doctrine of preemption is also based on the supremacy clause. The doctrine of preemption, preempts the state laws whenever there is a conflict in laws. The federal court can order the state courts if it thinks that its behavior is in conflict with the federal law.
The correct answer is A. While the states are free to make their own laws they cannot make laws that violate the constitution. For example a state cant legalize murder.
