Africans primarily traded with merchants along trans-saharan trade routes.

Arab merchants, is the right answer.

Explanation:

The trans-Saharan trade was not simply a commercial aspect, but it was related to Western Africa to the Mediterranean world on the rational level, besides. The medieval Arab geographers get to know sub-Saharan Africa by the stories of traders. The trans-Saharan trade was one of the main reason for the development of African empires. The people of African empires essentially traded with Arab merchants along this trade route.

i think it's a)sparta