Because thats their tradition
Can't answer this, since we don't have the article. If there are details about how black people in the north were freed from slavery in most states, while slavery was still allowed in the south, you could use that.
A. Gold
The rise of the kingdom of ghana was aided greatly by its abundant supply of gold
The policy was ended in 1921 because it was not successful. ... to feed and supply the hungry Red Army of Bolsheviks during the Russian Civil War. to move towards complete communism. War communism was largely successful at its primary purpose of aiding the Red Army in halting the advance of the White Army and in reclaiming most of the territory of the former Russian Empire thereafter.
A would be the best choice