I would say sea level but again im failing my grade idk 
but i think its sea level
 
        
                    
             
        
        
        
B. More drastic change than a point mutation
        
                    
             
        
        
        
Im not understanding what you are trying to ask in the question.
Is there answer choices?
Is there a paragraph to go with it?
 
        
             
        
        
        
Answer:
At sea level, air pressure is greatest because it is caused by the weight of the entire column of atmosphere at that altitude over that location. As altitude increases, the column of atmosphere gets shorter, and so less weight is pressing down at a given altitude, so atmospheric pressure is reduced.