How Did Spain Justify Enslaving Native Americans

How did Spain justify enslaving Native Americans?

A) The Spanish believed that enslavement could liberate Native Americans from their backwardness and savagery and introduce them to Christian civilization.
B) Pope Alexander VI had approved Spanish slavery but banned slavery in Portuguese holdings in the New World.
C) The writings of Bartolomé de Las Casas explained that the Bible approved slavery and that therefore it was acceptable.
D) If England and France were to be defeated in the quest for empire, Spain needed to take a step they had avoided-imposing slavery upon the native population.
E) The Spanish actually never enslaved Native Americans; the charge that they did was simply part of the Black Legend spread by the English and other enemies.