Concept:Protective functions of forests help safeguard the environment, such as soil, air, and nearby land.Explanation:Soil conservation is a protective role because forest roots hold the soil in place.Serving as a windbreak is protective because trees reduce the force of wind on farms and settlements.Purification of air is protective because trees absorb carbon dioxide and release oxygen.Source of firewood is not a protective role. It is an economic or productive use of forest resources.Answer:D. source of firewood