Which act repealed the Missouri Compromise and allowed slavery to be settled by popular sovereignty?

The Kansas-Nebraska Act of 1854 is the correct choice because it specifically repealed the Missouri Compromise, which had previously established a line beyond which slavery was prohibited in the western territories. The Kansas-Nebraska Act introduced the concept of popular sovereignty, allowing the settlers in those territories to determine for themselves whether they would allow slavery or not. This act played a significant role in escalating tensions between pro-slavery and anti-slavery factions, ultimately contributing to the events leading up to the Civil War.

The other acts and cases listed do not align with this specific function. The Compromise of 1850 was a series of measures designed to ease tensions over slavery but did not repeal the Missouri Compromise or institute popular sovereignty in the same way. Dred Scott v. Sandford was a Supreme Court case that addressed the legal status of enslaved individuals but occurred after the Kansas-Nebraska Act and did not involve the repeal or establishment of popular sovereignty in the territories. The Fugitive Slave Law of 1850 was part of the Compromise of 1850 and focused on the capture and return of escaped enslaved people, rather than addressing territorial governance related to slavery.