Answer:
D. A state is not allowed to tax federal money because federal law is superior.
Explanation:
The federal supremacy or Supremacy Clause is a principle found in Article VI of the U.S. Constitution, which establishes that all federal laws are superior and therefore, in case of a conflict between federal and state laws, the federal law must prevail, this means that the scope of the state laws is limited by the federal's laws, and due to this principle, a state is not allowed to tax federal money.
