The Kansas-Nebraska Act and the Civil War

In the years leading up to the Civil War, several socio-political factors fueled tensions between the North and South, impacting the trajectory of American society. Among these factors, events such as the Mexican-American War, the publication of "Uncle Tom’s Cabin," and court decisions played crucial roles. Which of the following events is considered a significant catalyst that exemplifies the growing sectional conflict regarding the institution of slavery and contributed directly to the onset of the Civil War?