The answer you're looking for is c.
Answer:
a) through attrition and massive advances on several fronts
Explanation:
American Civil War or simply Civil War in the United States was a war (although Congress never issued a Declaration of War) waged in the United States from 1861 to 1865. As a result, among other things, a historical controversy over slavery and against of the attempts of the American federal executive to take powers that did not correspond to him in a constitutional manner, the war broke out in April 1861, when the forces of the Confederate States of America attacked Fort Sumter in South Carolina, shortly after President Abraham Lincoln assumed his position. The nationalists of the Union proclaimed loyalty to the Constitution of the United States. They clashed with secessionists from the Confederate States, who defended the rights of states to expand slavery.
