The slave trade was made up of what three different backgrounds of slaves?

Slave trade in the Atlantic was part of a system known as the Triangular Trade. On the first leg of their three-part journey, often called the Triangular Trade, European ships brought manufactured goods, weapons, even liquor to Africa in exchange for slaves; on the second, they transported African men, women, and children to the Americas to serve as slaves; and on the third leg, they exported to Europe the sugar, rum, cotton, and tobacco produced by the enslaved labor force.  

Explanation:

when in doubt choose c

it's what my teacher told my class when we were going into psats

i beleive that d is the right answer