Which of the Following Is Most Likely a Reason for the Slavery

Which of the following is most likely a reason for the slavery issue to take the form of a dispute over states' rights versus national supremacy?​ 

A)  The Great Depression prevailing at that time​ 
B) The radically different beliefs of people in different parts of the country 
C) The federal nature of the U.S. government 
D) The lack of importance given to the slavery issue by the Supreme Court 
E) The changing cultural conditions