The process of desertification can occur when

a-plants usually found in the desert replace tress that have been cut down

b-farmers use contour farming techniques

c-an area of forest is clear-cut

d-an area of forest is selectively cut

Desertification occurs due to a decrease in vegetation. This can happen naturally due to a drought or can be caused by human activities. The lack of plants can cause changes to the land. Plants help shade the soil, so when plants are removed, the soil will be exposed to the sun and will dry out more quickly. So, I would say C. An area of forest is clear cut.