A. a tree
you can first eliminate B. and C. to make it easier to choose an answer. then you can eliminate a generator because it would turn mechanical energy into electrical energy. a tree uses photosynthesis to convert light energy into chemical energy, using the sun as a source for the light energy and turning it into food (chemical energy)
 
        
                    
             
        
        
        
Answer: D 
Explanation: It never specifically mentions anything about having a hypothesis it’s just saying it works.