Answer:
Option: D. The Mali Empire
Explanation:
The spread of Islam into West Africa became possible because of the conversion of the kings in the Mali Kingdom. In its early period, the Mali Empire was a multi-ethnic state with various religious and cultural groups. The presence of the Muslim advisers and counsellors in the empire court led to the spread of Islam. In the 13th century, rulers became Muslim and made the empire into a Muslim state under Mansa Musa.