Although Portugal was the first to use African slaves, Spain first sent them to America
The members of Dadaist Artistic movement felt that the logic and reason behind capitalist society led to WWI. This belief they felt had led to irrationality and chaos in the society which eventually led to the war.
I believe it's A: capitalizing on the harsh post-war conditions in their countries.
I do not know the answer, but if I were to guess, that it would be the one about plantations.
Plantations were hotspots of manual labor, specifically slaves. And when slaves were outlawed the plantation owners lose there main source of “profit” (aka the need to not pay workers for manual labor and instead use that money to get more laborers) it seems like the logical answer to me.
Also using process of elimination we know that the war could have spilt the country in two. So the union was indeed saved.
C is the answer I believe to your question