Answer:
1. Slavery
2. Economy
3. Politics
Step-by-step explanation:
Long Explanation:
The south seceded from the union because the northern states were more industrialized and didn't need slaves because they had factory workers. The Southern states, though, required on more manual labor by slaves in plantation fields. This was the states' way of life. They're entire economy came from buying and selling slaves, as well as harvesting cotton and tobacco, which was only harvested by their slaves. The Northern states didn't see the problem with getting rid of slaves because they had no need for them, but the South did. During all of this tension, there was also political tension because with each new state being inducted into the US, more were banning slavery and allying themselves with the North. This made the South uneasy because they were outnumbered in the House of Representatives and the Senate for votes (because there were now more Northern States than Southern States), in which they could have everything stripped from them. The Republican party had also been voicing their concerns about abolishing slavery, so when Abe Lincoln got elected they were done.
Short explanation:
The South and North had different views about slavery and the North was moving to abolish it. The South used slaves for its economy and so was very defensive about preserving slavery. The South and North had different political views and when the South was outnumbered and underrepresented and knew things were going to go down hill fast for them, they seceded to preserve their way of life.