The correct answer is C. Gold.
Explanation
The western area of Africa including countries such as Mali or Ghana that created large empires has been known during history for a large number of gold mines, this fame brought many explorers from other continents, mainly Europe to obtain gold and other minerals and take advantage of them. But besides this, the African empires that are found there like the Empire of Mali, Ghana, Niger, Nigeria, among others, have used this resource to trade as they exchange gold for other products such as salt that were not common in the area. So, the correct answer is C. Gold.
