Which clause provides that the constitution shall be the supreme law of the land?

Supremacy clause

It establishes that the Constitution, federal laws made pursuant to it, and treaties made under its authority, constitute the supreme law of the land. It assures that the Constitution and federal laws and treaties take precedence over state law  

Correct

Explanation:

The Supremacy Clause ensures that the Constitution is the supreme law of the land and the foundation of government.  The Supremacy Clause establishes that the US Constitution is above any state law enacted or other law that is passed.  Any other laws and government actions must be in accordance with the nation's Constitution. The Supremacy Clause is the second clause of Article VI of the Constitution.  It is stated as follows:

c. the dred scott v. sandford case,