Read the following paragraph from the section "The Abolitionist Movement Shifted The Balance." When considering leaving the Union, Southerners knew the North had an overwhelming advantage in population, industrial output and wealth. Still, many were eager to forge a future separate from what they saw as political and economic interference from Northern interests. As one state after another left the Union in 1860 and 1861, many Southerners believed they were doing the only thing they could to preserve their economy and their way of life, one based on slavery. How does the first sentence contribute to the development of the article's CENTRAL ideas? A It emphasizes what the South was willing to risk to preserve a cotton- and slavery-based economy. B It details the primary factors that eventually caused the Union to defeat the South in the Civil War. C It highlights the problems that the South was facing due to economic interference from Northern states. D It introduces a contrast between the North's industrial economy and the South's agricultural economy.