The answer is "C) slaves"
At that time, a new phase of African Islamization of the slave demand generated by the transatlantic slave trade resulted in the emergence of new states along the African coast and the mulsuman mercantile elites. Some of the slaves sold were also Muslims, who could be considered "impure" due to the coexistence of polytheistic rituals with Islamic practices. At that time, there was a strong relationship between commerce and religion, which led to its expansion.
