The correct answer is: A. It extends across the continent from the Mediterranean Sea to the Red Sea.
The Sahel region's geographical position, acting as a transitional zone between the Sahara Desert to the north and the more humid savannas to the south, facilitated trade routes that connected various regions, including trade between North Africa and the rest of Sub-Saharan Africa. This location allowed for trade across the continent, making it an important area for commerce.