Answer: D) Wars of independence killed most of the Native American population.
It is likely that both option C and D played some part in the decline of the population shown in the graph. European diseases killed an enormous amount of indigenous people, as they had no resistance or immunity to them. However, diseases were particularly destructive upon the first meeting with Europeans. Columbus arrived to America in 1492, and most people were contacted within the next few decades (the Europeans reached the Aztec empire in 1521, and the Inca in 1526). Therefore, the decline that continued up until 1590 was most likely due to conflicts and wars of independence.
