The West African city described in the list is D. Timbuktu.
Timbuktu was indeed one of the oldest known cities in sub-Saharan Africa and served as a significant trading post on the Trans-Saharan trade routes. It was also a center of Islamic learning, particularly during the Mali Empire, and it was conquered by Sunni Ali, the ruler of the Songhai Empire, after a seven-month siege in the 15th century.