Answer:
D. merchants
Step-by-step explanation:
in the past, there is one popular trade routes called the silk road. The silk road was a trade path that connected Africa, Europe, and Asia.
A lot of merchants from these three continent often gathered together to socialize. When they do that, cultural exchanges occurred between the merchants, and some teachings about Islam were spread to the merchants and brought in to their country of origin. After coming back, those merchants spread the religion to the locals and contributed to the spread of Islam in Afro-Eurasia.