How did the issue of Slavery lead towards the Civil War?

a
Higher tariffs in the north led to an increased demand for slaves. Because the North could not afford slaves they went to war with the South for better prices.
b
The majority of the southern economy depended on slave labor. Losing slavery would have hurt the southern economy so badly that the South fought to keep it.
c
Slavery led towards the Civil War because the North sided with Mexico and allowed run away slaves to stay in Mexico. This angered the South and led to war.
d
The only reason slavery led towards the Civil War is because the North felt it was morally wrong and that war was the only way to free the slaves.