It's C, because feds are for the, powerful big federal union centralized "american" national government.
This contradicts D, so it can not be D, since feds were NOT the kind of people to say. "Hey stop !!! The American government is bullying my Virginia." No virigina does not have soveringy in the eyes of feds. The USA is the powerful nation holding the states - The alliance of states is stronger than the individual power of states.
It's important to recognize that some colonists and early Americans did not see them selves as together as one. " We are not Americans as a nation, but only a region." Like Europe with all their different states and nations.
It also says all past " But if the union...." Obvious for what I think.
Direct causality can be drawn between nationalism and war. ... Nationalist groups within a state who desire their own independent state, (one organised to include their ethnic or cultural identity, for example), may conduct regular or irregular warfare in order to forcibly persuade a state to grant them independence
The enforcement Acts were acts recommended by Grant and imposeed by congress to try to protect black voters from intimidation and violence.