The correct answer is C.
There was a slave system that had existed in West Africa prior to the Age of Exploration and Conquest. However, the slave system that existed bore no resemblance to that which developed in the New World in the 18th- and 19th-centuries. Firstly, one would not be in bondage for a lifetime. Secondly, the slave system more closely resembled a system of apprenticeship. A young man would be captured from a neighboring tribe, as part of the spoils of war, then kept as a slave for a number of years. During those years, he would learn a skill, then would be freed and allowed to apply that skill toward making a living for himself and his family. Thirdly, there is no evidence showing that the system of cruel and inhumane retribution that existed in the New World also existed in West Africa. There was also no concerted effort to keep slaves in states of ignorance and degradation.
West Africans who were captured and brought to the New World were followers of Islam, not Christianity. The Kingdom of Mali, for example, accepted Islam in the early fourteenth century. Islam reached West Africa as a result of trade with North African states.
Lastly, as with many societies, there were class divisions in West African kingdoms. Kingdoms are defined by class division. Each kingdom was comprised of village states headed by a particular family. Village states were formed by clans, or families, who shared common ancestry. Each African king had a group of ministers and advisers. Strong village states, which were comprised of a strong military, good leadership, and ample resources (e.g., livestock) could grow into powerful kingdoms. The kingdoms of Mali and Songhay were characterized by such strength.
Now, let's focus on why "C" is the correct answer. The first Africans were brought to the New World in the 16th-century. The Norton Anthology of American Literature and John Hope Franklin's From Slavery to Freedom: A History of African Americans claim that the first slaves were brought to Hispaniola (the island now comprised of both Haiti and the Dominican Republic) in 1502, and into other parts of Latin America in the second decade of the sixteenth century. Most West Africans were taken to Brazil and the Caribbean.
Brazil, a nation which currently has the largest population of black people outside of Nigeria, received about forty-five percent of the slaves transported across the Atlantic. Islands in the Caribbean, particularly the Barbados, which had a thriving sugar trade, received another forty-five percent. The thirteen colonies only received around five percent, while the other five percent of slaves were scattered throughout the Americas.
The response in Answer C is slightly misleading. For, the Caribbean is, of course, a part of North America. Slaves who first disembarked in the Barbados might have been shipped North to other thriving commercial colonies, such as South Carolina or Virginia. By 1834, the British abolished slavery in all of its colonies. Demand for slaves declined in Virginia, though not in South Carolina, in the 1820s as a result of dropping prices for tobacco. As a result, many Virginia slaves were frequently shipped to the Deep South (e.g., East Texas, Mississippi, Arkansas, and Alabama) where the cotton trade thrived.