The correct answer is: d) All of the above.
Jhum cultivation is a traditional form of shifting cultivation practiced in the hills of Assam. It involves clearing a patch of forest, burning the vegetation, and then planting crops on the ash-enriched soil. After a few years, the soil becomes depleted and the farmer moves on to clear a new patch of forest. This practice can lead to soil erosion, as the exposed soil is easily washed away by rain.
Overgrazing is another major cause of soil erosion. When too many animals graze on a piece of land, they can trample the vegetation and compact the soil. This makes it difficult for water to penetrate the soil, and can lead to erosion.
Deforestation is also a major cause of soil erosion. When trees are cut down, the roots that hold the soil in place are removed. This can lead to the soil being washed away by rain or blown away by wind.
All of these practices can contribute to soil erosion, which is a major concern in Assam. Soil erosion can lead to a loss of fertile land, a decrease in crop yields, and an increase in flooding. It can also have a negative impact on the environment, as it can lead to the loss of biodiversity and the degradation of water quality.