The correct answer is: Option A. The Confederacy lost against the union and failed to help the Native Americans who had signed treaties with them before the war, leaving them devastated.
Both the Union and the Confederacy had signed treaties with Native Amercian tribes by 1861. Regarding the Confederacy, The Cherokee, Creek, Choctaw, Chicasaw, and Seminole were enlisted to form an alliance. These tribes suffered from internal disputes and some found themselves violating their own traditional values, as they often had to fight against opposing tribes.
By the end of the war, many indian encampment had been devastated, and the ones standing got little to no attention from the former Confederacy, especially the Choctaw, who were left ignored and unsupplied for most of the war.