The statement that accurately describes how the supremacy clause has made a positive contribution to the concept of federalism is:
The supremacy clause has allowed the Supreme Court to resolve conflicts when both the national and state governments are exercising legitimate, but conflicting, powers.
This reflects how the supremacy clause, found in Article VI of the U.S. Constitution, establishes that federal law takes precedence over state law, allowing for a judicial mechanism to resolve disputes between different levels of government.