The correct answer is: a) Jhum.
Jhum cultivation, also known as shifting cultivation, slash-and-burn agriculture, or swidden agriculture, is a traditional agricultural system in which farmers clear a piece of land by cutting and burning trees and then cultivate crops on the land for a few years. After a few years, the land is left fallow to regenerate, and the farmers move on to clear a new piece of land.
Jhum cultivation is a sustainable agricultural system when it is practiced in a traditional way. However, when it is practiced on a large scale, it can lead to deforestation and soil erosion.
Taunya is a system of agroforestry in which trees are planted along with crops. This system is used in some parts of Southeast Asia, including Assam.
Terrace farming is a system of agriculture in which fields are built on terraces on hillsides. This system is used in some parts of the world, including the Himalayas.
Contour farming is a system of agriculture in which fields are planted along the contours of the land. This system is used to prevent soil erosion.