If a State Supreme Court Decides a Case Based Solely

If a state supreme court decides a case based solely on state law, what impact can the U.S. Supreme Court have on the decision?

A) Overturn the case based on its own interpretation of state law
B) Declare the state law unconstitutional so that the case has to go back to lower state courts
C) Review the decision and use it as a precedent for federal cases
D) Using the theory of stare decisis, change the decision to meet federal guidelines
E) Nothing, as the U.S. Supreme Court can only rule on federal cases or constitutional questions