This Should Help a Little:
A largely semi-arid belt of barren, sandy and rock-strewn land, the Sahel marks the physical and cultural transition between the continent's more fertile tropical regions to the south and its desert in the north. ... The Sahel also suffers from ethno-religious tensions, political instability, poverty and natural disasters.
North is the direction you're looking for.
Answer and Explanation:
Student B is correct, because Mercury is, in fact, possible to be visualized during the morning or evening twilight, that is, just after sunset, or just after sunrise, as times are necessary for the planet earth it has the right lighting to visualize it.
Student C is the one that is most incorrect, because at midnight the planet earth has very low luminosity so that Mercury can be visualized. Since it needs a low illumination, however existent for the planet Mercury to be seen.
The ozone layer. The gas it is made of is formed by 3 oxygen atoms.
