Answer:
The correct option is c
Step-by-step explanation:
Reforestation is the process of planting new trees in a forest that has experienced huge depletion in the population of trees that use to be present in the forest (this is mostly caused by deforestation). Reforestation helps in maintaining the habitat in the forest, hence assists in maintaining/improving the environment.
Shelter belting is the process of planting trees (in the form of a shade) in a row usually to protect plants and animals from extreme temperatures (very cold or very hot). Shelter belting assists in maintaining/improving the environment by providing shades for plants and animals.
Overgrazing is the excessive grazing of a "grassland" by livestock without giving the "depleted grassland" enough time to recover. Overgrazing damages the soil and leads to erosion hence overgrazing may to deterioration of the environment.
Contour ploughing is the ploughing of a slope of the land usually to reduce soil erosion. The prevention of soil erosion assists in maintaining the environment.