Answer:
D) Slavery
Explanation: The north and south were split on whether or not the should have slavery. The south seceded from the states and became the confederacy. The north became the union. After 4 years of continual war, the union won, and slavery was abolished. The south's economy crumbled, and it eventually led to the creation of the Klux Klan. Even in the north, black Americans were still treated differently after the civil war. They were segregated from others until Martin Luther king jr's speech led to the end of segregation in 1964.