The correct answer A) passage of the Missouri Compromise.
What best illustrates the dichotomy of American society's attitudes about slavery in the early 19th century is the passage of the Missouri Compromise.
The context of the Missouri Compromise of 1820 was that there were many problems with slavery in the states. Some approved and depended on slavery, others -mostly the Northern states- disapproved and supported desegregation. In 1819, Missouri asked to enter the Union as a slave state, breaking the balance between supporters and non-supporters. By passing the Missouri compromise, the US Congress to have an option to sooth the complicated situation. It granted the Missouri request, and at the same time, Main was admitted as a free state.