Final answer:
Trade, particularly the trans-Saharan trade routes, had the greatest influence over the economic activities of residents of the Sahel region.
Step-by-step explanation:
The factor that had the greatest influence over the economic activities of residents of the Sahel region was trade. The trans-Saharan trade routes played a vital role in the economic development of the region. The trade routes facilitated the exchange of goods, such as gold, salt, and other commodities, between West Africa and North Africa, which boosted economic activities and promoted cultural interaction.
The gold trade, in particular, had a significant impact on the economy of the Sahel region. The gold trade attracted merchants from North Africa, who established trading posts and commercial centers in the Sahel, contributing to the growth of towns and urbanization.
Additionally, the trade routes also stimulated the growth of agriculture and animal husbandry, as they provided opportunities for the exchange of agricultural products and livestock.