In the atmosphere, the density of air particles decreases with height, with more gas particles remaining near the surface of Earth. When only taking into account humidity, dry air is more dense than moist air because of molecular weights of the gases.
        
             
        
        
        
The answer to your question is B.
        
                    
             
        
        
        
Answer:
Explanation:
The skeletal system
The skeletal system works as a support structure for your body. It gives the body its shape, allowing  movement.
 
        
             
        
        
        
Answer:
The environment the moths lived in used to be unpolluted. This made dark moths rare. As the area where light moths were found became more polluted, the light moths became less common in the polluted/dark areas. Light Moths began to evolve after not being able to survive in dark forests, they began to get darker and blend in with the polluted area to be safe from predators.
Explanation:
 
        
             
        
        
        
C. Radioactivity 
is the answer 
and Uranium is an element that produces radioactivity