The correct answer is: B. Desertification.
Desertification is the degradation of land in arid, semi-arid and dry sub-humid areas. It is caused by a number of factors, including climate change, human activities, and natural disasters. Desertification can lead to a number of problems, including loss of biodiversity, soil erosion, and water scarcity.
Land fertility is the ability of soil to support plant growth. It is affected by a number of factors, including the type of soil, the climate, and the management practices used. Land fertility can be improved through a number of methods, including fertilization, irrigation, and crop rotation.
Ecosystem is a biological community of interacting organisms and their physical environment. Ecosystems can be classified into different types, based on their climate, vegetation, and other characteristics. Ecosystems are important because they provide a number of services to humans, including food, water, and clean air.
Vegetation is the plant life of a particular area. It is affected by a number of factors, including the climate, the soil, and the human activities. Vegetation can be improved through a number of methods, including planting trees, shrubs, and grasses.