Deforestation is the a. cutting down or burning of all the trees in a forested area b. replanting of trees in an area where trees were cut down c. managing of forests for the benefit of people d. adding of nutrients to topsoil in order to make land more arable

A. cutting down or burning of all the trees in a forested area 

A. cutting down or burning of all the trees in a forested area

Explanation:

Deforestation includes the cutting and burning down of the natural vegetation by the man for his greedy needs and thereby depleting the land and creating natural hazards like the desertification, soil erosion and the destruction of natural habitations of flora and fauna.

Answer collision and mountain formation;