Concept:The practice of growing trees and arable crops together on the same land is known as the taungya system.Explanation:The taungya system is a method where farmers raise arable crops between rows of young trees.This is usually done in the early years of a forest plantation.It allows both trees and crops to use the same piece of land simultaneously.Other options do not match this definition.Mixed farming involves crops and livestock, forestry involves only trees, and ley farming involves alternating grass with crops.Answer:D. taungya system