A. Africa
According to a 200 census, 50.7% of Brazil consists of blacks or mixed-race citizens. As many know, Spain was never the victim of slavery but more of an enforcer of slavery. Africans often labored for and sold by the Spanish, since they participated in the slave trade. Holland, a Dutch nation, and Portugal also participated in slave trade so we can also eliminate these options. Lastly we can refer to our own history (or at least my own history), where Africans were used as slaves and sold like property by wealthy white men. Hope this helps!