Which statement most accurately describes the relationship between state governments and the federal government?

The correct answer is C. The supremacy clause of the Constitution ensures that it overrules state constitutions and laws that address the same matters.

Indeed, the Supremacy Clause is quite clear, in the event of a conflict between state and federal law, it is always federal law that prevails. The Supremacy Clause is the foundation of the entire American political and legal system.  

The other answers are incorrect: Concurrent Powers are concurrent because they can be exercised both by federal and state governments. State courts are always required by law to abide by any US Supreme Court rulings. Reserved power cannot be held by both the federal and state governments. There are set of powers that are separately reserved for states and others which are reserved to the federal government.

answer; by working independently, the states have a high likelihood of developing innovative solutions that can be employed in other states;