In Erie Railroad V

In Erie Railroad v. Tompkins, where Tompkins was hit by a New York train while in Pennsylvania, regarding the application of common law in a diversity of citizenship case in federal district court, the Supreme Court decided that:

A) federal courts must follow procedural law of the state in which it is located
B) federal courts may apply either state or federal common law to resolve a case before it
C) the common law of the appropriate state must be applied in cases in federal courts
D) federal courts must follow federal common law in all disputes before them
E) none of the other choices are correct