Answer: B. silent trade.
Explanation: The Soninke people, who lived in West Africa in what is now Mali, acquired the salt that they needed through a process called "silent trade." This involved traders from the north, who had salt, leaving the salt at a designated spot in the desert. The Soninke, who had gold, would come to the spot and leave gold in exchange for the salt, but without any direct contact or communication between the traders. This helped to maintain peaceful trade relations between the two groups, as they did not share a common language and had different cultural practices.