How was the Civil War a test of state's rights versus national government rights?

A. The Southern states believed they had the right to leave the United States. The U.S. government agreed and allowed them to secede the United States.

B. The Northern states believed they had the right to leave the United States. The U.S. government agreed and allowed them to secede the United States.

C. The Southern states believed they had the right to leave the United States. The U.S. government did not agree and used military force to impose its will on the states.

D. The Northern states believed they had the right to leave the United States. The U.S. government did not agree and used military force to impose its will on the states.