Please help il mark brainlist what was a major cause of the Civil War?

A ) Northern and Southerns disagreed over the spread of slavery.
B ) Southerns wanted John Browne to receive a fair trail.
C ) Northern and Southerns belonged to different political parties.
D ) Northern's wanted Stephen Douglas to win the election of 1860.

A) Northern and Southerners disagreed over the spread of slavery.

Explanation:

"What led to the outbreak of the bloodiest conflict in the history of North America? A common explanation is that the Civil War was fought over the moral issue of slavery. In fact, it was the economics of slavery and political control of that system that was central to the conflict. A key issue was states' rights."

It helps someone to concentrate..on something.