Why did american colonists import millions of africans to work as slaves in the colonies?

The practice of selective incorporation means that the bill of rights will

    which of the following was anecological  result of european exploration from 1400 to 1800?   a.  increased trade with east asia      b.  the spread of epidemic diseases      c.  expansion of english territory      d.  the spread of christianity

The answer because i don’t know it someone