How did the kansas-nebraska act cause more violence?

Deciding whether a territory would allow slavery or not based on a vote of the people in the territories led to slavery supporters and abolitionists both rushing to the region in order to vote on the issue.  This led to an outbreak of violence between the settlers.

Explanation:

The Kansas-Nebraska Act was enacted by Congress in 1854. It granted popular sovereignty to the people in the Kansas and Nebraska territories, letting them decide whether they'd allow slavery.  In essence, this made the Kansas-Nebraska act a repeal of the Missouri Compromise of 1820, which had said there would be no slavery north of latitude 36°30´ except for Missouri.

After the passage of the Kansas-Nebraska Act, pro-slavery and anti-slavery settlers rushed into Kansas to try to sway the outcome of the issue, and violence between the two sides occurred.  The term "bleeding Kansas" was used because of the bloodshed.  

i believe the answer is a