Which country played the biggest role at the beginning of the Atlantic slave trade?

Portugal

The most active European nation in the trans-Atlantic slave trade was Portugal, which used the forced labor of Africans in their Latin American colonies in present-day Brazil. Almost 3.9 million enslaved Africans were forced to embark on Portuguese ships.

Explanation:

increases in demand are shown by a shift to the right in the demand curve. this could be caused by a number of factors, including a rise in income, a rise in the price of a substitute or a fall in the price of a complement.

which the answer is:

b