The Primary Reason That European Planters in the Americas Came

The primary reason that European planters in the Americas came to rely on the labor of African slaves was that

A) Europeans regarded Africans as racially inferior to other races and viewed them as the only people fit for enslavement.
B) Africans were generally more meek and docile than Native Americans,who refused to allow themselves to be enslaved.
C) the importation of Old World diseases and the harsh labor demands of European conquistadores devastated the native populations of the Americas.
D) unlike African societies,Native American societies were too well organized and sophisticated for Europeans to conquer until long after the discovery of the Americas.