Ventilation systems are needed in a <span>multicellular organism to actually obtain oxygen and give out carbon dioxide. Without this ventilation system, it would be very difficult for multicellular organisms to survive. It has been also observed that surface diffusion is not enough for a multicellular organism to breath.</span>
        
             
        
        
        
Answer:
c.All are halogens, so they are not very chemically active,
 
        
                    
             
        
        
        
X-rays are the radiation that allows us to see through the skin to visualize bones
        
             
        
        
        
Fill a graduated cylinder to 10mL, place the rock inside and calculate the difference in mL.
        
             
        
        
        
Answer: We need DNA to reproduce and it's unique due in part to recombination. recombination is traded between the chromosomes that make up a pair.
Explanation: