The correct answer to this open question is the following.
The three major differences between the North and the South that helped lead to the Civil War were the following.
1.- Northern states did not support slavery. Southern states authorized slavery.
2.- The economy of the northern states was much more industrialized. The North had large factories and fabrics in many states. These allowed them to produce more and better goods and better prices, including weapons and supplies. On the other hand, the South absolutely depended on agriculture and on slaves that worked long hours to produce the crops needed for trade and that were exported to Europe.
3.- Sothern people were very religious people, meanwhile, northerners were more moderate about religious beliefs.