Concept:The carbon cycle is maintained when carbon dioxide removed from the air is balanced by processes that return it.Explanation:Bush burning releases carbon dioxide into the air instead of maintaining balance.Felling of trees reduces the number of plants that absorb carbon dioxide.Release of fumes from factories adds extra carbon dioxide to the atmosphere.Replanting trees felled as timber replaces trees so that photosynthesis can continue to absorb carbon dioxide.Therefore, replanting trees helps maintain the carbon cycle.Answer:D. Replanting of trees felled as timber