Answer:
B. The Supreme Court can declare a state law unconstitutional.
Step-by-step explanation:
The Supremacy Clause establishes that all federal laws are the supreme law of the land and therefore all states, federal officers and judges are bound by it. So, if a state law is in conflict with federal law, the Supreme Court, which has the power of Judicial Review, can declare such state law unconstitutional because federal laws are the ones that must prevail.