Drought and leaching have continued to the process a major environmental challenge in africa a. animal endangerment. b. reforestation c. desertification d. air pollution

The answer is C. Desertification. 

Desertification is a kind of land degradation where fertile land becomes a desert. The major causes of desertification is drought, which is a prolonged period of little to no rainfall and leaching. Both drought and leaching promotes erosion which is part of the process of desertification. 

Answer they are produced by collision of tectonic plates;

Earthquake waves that vibrate from side to side and up and down only through solids are known as "seismic waves."hope my answer has you : )