The correct answer is D) panned from rivers.
The gold that miners in the Sahel traded for salt was panned from rivers.
The Sahel is the region in Africa between the Shara Desert and Sudanian Savanah. It crosses the territory of Senegal, Mauritania, Mali, Argelia, Nigeria, Cameroon, Chad, Sudan, and Ethiopia.
The Sahelian kingdoms inhabited these lands form the 9th to the 18th centuries. They controlled the trade in the trans-Saharan routes. The taxation of trade was the most important factor in the development of kingdoms. Many parts had raw materials and valuable minerals such as gold that was panned from the rivers and was traded for salt.
