Answer:
Mitochondria convert chemical energy, in the form of a chemical called adenosine triphosphate or ATP for short. ATP is an energy currency that every cell in our body can use. ... Electrons are passed between the complexes of the electron transport chain and enable the cells to convert energy.
so it's 2nd (light to glucose)
 
        
             
        
        
        
The skeletal system<span> performs vital </span>functions<span>— support, movement, protection, blood cell production, calcium storage and endocrine regulation — that enable us to survive.</span>
        
             
        
        
        
Genetics, double helix, cells
        
                    
             
        
        
        
Chemoreceptors is the answer