Answer:
C. The native populations of the Caribbean had been decimated by European diseases.
Step-by-step explanation:
The Europeans tried to enslave the Americans initially. However, the native people did not have the genetic immunities to conquer the diseases, and this led to the catastrophic mortality of the population in the natives of America. Because of this reason, they were not fit for slavery.
The Africans, on the contrary, had the needed immunities, and the Europeans discovered this in the 1500s during the trade in the Atlantic region, and they, therefore, developed rapidly and filled the demands of required slavery.