The answer is B. both need food and air 
        
             
        
        
        
The side of a mountain range that faces the wind often receives more moisture then the downwind of the same range
        
             
        
        
        
The atria and ventricles work together, alternately contracting and relaxing to pump blood through your heart. ... The electrical activity spreads through the walls of the atria and causes them to contract. This forces blood into the ventricles. The SA node sets the rate and rhythm of your heartbeat.