Respuesta :
The correct answer is C. Slavery had been abolished.
Explanation:
The American Civil War (1861-1865) was one of the most relevant wars in the U.S.; in which The Union (Northern states) fought against the Confederation or the states from the South that seceded.
One of the most relevant and positive outcomes of the war was the abolition of slavery, which was part of the causes of the war. Indeed, in 1863 during the war, the Emancipation Proclamation was issued by Lincoln and through this .slaves in the south were declared free. Also, when the war ended as The Union defeated the Confederate States the Thirteen Amendment that abolished slavery in all the U.S. territory was approved. Thus, the one that was not a negative consequence of the Civil War is "slavery had been abolished".