The best and most correct answer among the choices provided by your question is the first choice or letter A which states that "The Portuguese and Spanish were the first Europeans to seek Africans slaves to work in their colonies."
The transatlantic slave trade began during the 15th century when Portugal, and subsequently other European kingdoms, were finally able to expand overseas and reach Africa. The Portuguese first began to kidnap people from the west coast of Africa and to take those they enslaved back to Europe.
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