A, Slaves provided much of the labor on plantations that grew cash crops would be the answer I would go with. Most slaves worked in crop fields, and iron working didn't become prominent in the US until the industrial revolution about 10 years after the Civil War. I cannot say I'm 100% certain, but the others to me don't seem to make sense when looking at the situation.
NSZZ Solidarność is Poland's trade union. It was formed in 1989 to rebel against the communism in the country. In the end it became a compromise of Independence of individual trade throughout the country.
