Final answer:
The West African trading empires, including Ghana, Mali, and Songhai, grew wealthy by controlling trade routes and resources, taxing trade, and leveraging diplomatic relations. The correct option is B.
Step-by-step explanation:
The West African trading empires grew and became wealthy primarily through monopolizing trade routes and controlling valuable resources such as gold, salt, and slaves.
The empires of Ghana, Mali, and Songhai were particularly adept at leveraging their strategic locations to facilitate and tax trade across the Sahara, connecting the Mediterranean world, Europe, Near East, southwest Asia, and beyond. They also imposed taxes on goods transported through their territories, which further increased their wealth.
Moreover, the cultural unification of the region under Islam and the establishment of peaceful diplomatic relations aided in the consolidation of their power and expansion of their economic interests.
Hence, Option B is correct.