Answer:a stationary front.
Explanation: 
they allow repeated thunderstorms to move across the same area.
 
        
                    
             
        
        
        
The answer is lateralization of brain function. This is the predisposition for some neural functions or cognitive processes to be more prevailing in one hemisphere than the other. The medial longitudinal fissure divides the human brain into two separate cerebral hemispheres, connected by the corpus callosum.
        
             
        
        
        
"Different substances sometimes have the same chemical formula, such as glucose and fructose, but they have different components so they act differently."
        
                    
             
        
        
        
The answer would be 502 grams because of the law of conservation of mass, you can't create or destroy mass so then 2 grams plus 500 grams is 502. I am 100% positive that B is correct.