The correct answer is: D. Shift cultivation.
Shift cultivation is a traditional agricultural system in which land is cleared for cultivation by cutting and burning trees and then abandoned after a few years. The land is then allowed to regenerate for a period of time before being cleared again. This system is often used in areas with low population density and abundant forest resources.
Pyrolysis is a thermochemical decomposition of organic matter at elevated temperatures in the absence of oxygen. It is a process that can be used to produce a variety of products, including charcoal, bio-oil, and syngas.
Jhum is a type of shifting cultivation practiced in the hills of Southeast Asia. It involves clearing a small area of forest, burning the vegetation, and then planting crops on the ash-enriched soil. The land is then abandoned after a few years and allowed to regenerate.
Taungya is a system of agroforestry in which crops are grown in association with trees. It is often used in areas where there is a shortage of land for agriculture. The trees provide shade for the crops and help to prevent soil erosion.
In conclusion, the correct answer to the question “The cutting down of trees and setting them on fire and raising crops on the resulting ash is called:” is D. Shift cultivation.