How did disagreement over slavery in the 1850's lead to the break up of the united staes?

March 1, 1836- texas declares independence from mexico march 6, 1836- mexico wins the battle of the alamo april 21, 1836- texas wins the battle of san jacinto which of these should come next in the timeline? a) mexican-american war begins b) civil war begins in the u.s. c) sam houston named president of texas d) texas becomes the 28th state of the u.s. eliminate