Why did South Carolinians support the concept of popular sovereignty?

1.It advanced the plantation system in Kansas.
2.It was a plan, introduced by a southerner, which was supported in the North and the South.
3.It showed that compromise was a peaceful way to solve problems.
4.It allowed for slavery to potentially expand above the line of the Missouri Compromise.

4. It allowed for slavery to potentially expand above the line of the Missouri Compromise.