Which is an accurate statement about slavery in the United States? A. Laws guaranteeing their rights made it possible for runaway slaves to live openly in northern states. B. Most slaves in the United States worked in the coal mines of Appalachia or the mills of New England. C. Slavery had existed for millennia, but only the United States used slaves for farm labor. D. Despite a well-meaning movement by whites to send freed blacks to Africa, most did not want to go.