Final answer:
John C. Calhoun believed that if slavery were abolished, A) economic prosperity in those states would decline, as the Southern economy was heavily dependent on slave labor for key crops like cotton.
Step-by-step explanation:
According to South Carolina political leader John C. Calhoun, in states where slavery was abolished, A. Economic prosperity would decline. Calhoun was a staunch defender of slavery and the antebellum Southern economy. His belief was that the Southern economy, which was deeply reliant on slave labor for the production of crops such as cotton, rice, and tobacco, would suffer without the institution of slavery. The profitability of cotton, in particular, was intimately linked to the use of slave labor.
Pro-slavery advocates, including Calhoun, argued that slavery provided not just economic benefits but also a sense of order and social cohesion. They contended that without slavery, the Southern states would face economic ruin and social upheaval. The views of Calhoun and others were in direct opposition to the Northern perspective, where slavery was seen as degrading to the dignity of labor and a hindrance to social and economic mobility, particularly for non-slaveholders.