Question

Many villages in the Sahel have been settled _____.

A.) on the banks of the two main rivers
B.) near forested areas
C.) at the edge of the Sahara
D.) outside of cities

Answer 1

I am pretty sure that many villages in the Sahel have been settled at the edge of the Sahara. I choose the option C because It seems to me that you are referring era of Sahelian Kingdoms and If so, most odf them were settled at the edge of the Sahara. Do hope you will find it helpful!
Regards.