Answer:
Option (3) southern states threatened to secede from the Union over the issue of slavery
Explanation:
By the 18th century, the United States faced a number of issues. For example, the slave trade was one of the issues that resulted in the state being brought into turmoil. This was because the United States was already divided into two - the Northern region and the Southern region. The Northern region was the one region that still held to slave trade despite it being abolished. The South, offered slaves freedom. Thus, the movement of he slaves from the North to the South was a major issue. Thus, the war was over the trade as the north though it was suffering due to the decrease in slave labor.