What Was the Primary Reason Europeans Were Proponents of the Slave

What was the primary reason Europeans were proponents of the slave trade?

A) Africans were thought of as little more than chattel.
B) Enslaved people compensated for the labor shortages in the New World brought on by annihilation of Native Americans.
C) Slavery was an outgrowth of the Industrial Revolution, and workers were needed for factories.
D) European traders sailing to the Americas needed any possible cargo they could find, and slavery was the most profitable solution.
E) Cities in the New World needed to be populated, and too few Europeans were voluntarily leaving for the colonies.