Whats The Options For This Answer ?
        
                    
             
        
        
        
Answer: E.  reforestation
Explanation:
Reforestation is a process of planting trees in an area so as to conserve the land as future forest. According to the given situation, reforestation is the practice which can be used by the biologists to grow nitrogen fixing plants in an area so as to increase the nutrient concentration of the soil which have been depleted. 
 
        
                    
             
        
        
        
Well it surely isn't nuclear, or electrical. It's not radiant either.. So the only answer is chemical.
        
             
        
        
        
Cutting down trees in the forest to make furniture because trees produce oxygen
        
                    
             
        
        
        
C is your answer so pick c