Option: d. Â the arrival of Europeans
Explanation:
The nature of slavery changed when European arrived in Africa. The first Europeans to reach in Africa around the West African coast were the Portuguese. The Portuguese arrived in Africa during the 15th century, and later the Dutch, British, and French followed. In the beginning, Europeans traders became interested in gold and ivory. Later traders kidnapped Africans and sold in Europe. During the 17th century, slavery system became part of the economy. The plantation owners required slaves in sugar and tobacco plantation to maintain the stability of the demands by European for the products. Â