Answer: 4. Kilwa
Step-by-step explanation:
Kilwa was a city located in what is now Tanzania and was founded by people from Arabia and Persia. With the founders being Muslim, the location converted to Islam and spoke a mixed language of Arabic and local dialects.
Kilwa's position by the coast made it a great trade city where merchants exported items such as gold, copper and rhino horn and sometimes rulers even minted gold coins in foreign currencies so that people may trade more efficiently in the city.