A. the refusal of southern states to ratify the Thirteenth Amendment
Explanation:
Towards the American Civil war that lasted between 1861 to 1865. There was constant tension between the federal government and the Southern colonies on the issue of slavery.
Hence, given that thirteen amendments were about slavery abolition and which was not ratified by the south.
Therefore, the fight for the balance of power which is influenced by the issue of slavery led to the federal government's decision to divide the South in this way.
