Based on the options provided, the most logical conclusion that can be drawn is:
A) The expansion of the United States increased sectional tensions between the states.
This conclusion is generally supported by historical evidence, as the expansion of U.S. territory often raised conflicts over the extension of slavery into new states and territories, leading to heightened sectional tensions between the Northern and Southern states. This was evident in events leading up to the Civil War, such as the Missouri Compromise, the Kansas-Nebraska Act, and various other legislative and social conflicts surrounding the issue of slavery and its expansion.
The other options can be argued against based on historical context:
B) The movement for the abolition of slavery did not grow significantly in the Southern states during this period; in fact, it was largely suppressed there.
C) The threat of European trade embargoes was not a primary driver for outlawing slavery in the United States; rather, it was primarily an internal political issue.
D) While popular sovereignty was proposed as a way to resolve conflicts over slavery, it often led to violence and further conflict (as seen in "Bleeding Kansas"), suggesting it did not effectively deescalate tensions.
Thus, A is the statement that aligns best with historical trends.