Which of the following best describes the practice of slavery at the time of the Dred Scott case?

(a) Slavery had expanded extensively across the continent, which made Northerners extremely nervous.

(b) Slavery had been banned almost everywhere, which made Southerners extremely nervous.

(c) There was a great deal of tension between the North and South over the practice of slavery.

(d) The North and South remained in agreement about the Missouri Compromise, which had settled the slavery issue.