The answer is B. Mountains.
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.
Answer:
True
Explanation:
Subduction occurs when an oceanic plate runs into a continental plate and slides beneath it. (I hope this helps)
A possible cause was a meteorite hit the earth. it caused many organisms to become extinct because it blocked out the Sun so plants couldn't grow and herbivores couldn't eat the plants and carnivores couldn't eat herbivores.