Im pretty sure you are talking about Sahel. If not my bad.
The correct answer is - b. the red sea.
The Red Sea is a sea located between the western coast of the Arabian Peninsula and the northeastern part of Africa, and it represents a natural border between them. It is a sea that has a linear appearance, with northwest-southeast direction. It is connected to the Mediterranean Sea through the Suez Canal, which is very important canal for the trade between Europe and North Africa with the Asian countries.
Cones, cylinders and spheres can have vertical cross-sections that are circles.
As the magma cools and solidifies, the convection currents will stop and the Earth will become geologically dead.