Which of the following had already existed in Africa before the Portuguese arrived? A. Widespread practice of Christianity
B. The Triangle trade
C. European colonialism
D. Extensive trade networks

D. Extensive trade networks

Explanation:

Trade in in raw materials as well as manufactured goods and other items was already established in Africa before the coming of the Europeans. There were already many trade routes by which African Kingdoms traded in diverse commodities in many renowned kingdoms of Africa before the Trans-Atlantic slave trade.

Trading was carried out on land and by waterways, these existing trade network enabled the Europeans to have access to Africa . Without these existing trade routes, the penetration of the Europeans would have been more challenging.