Answer: It is an amino acid that cannot be made by the body. It must be obtained from eating certain foods.
Explanation:
 
        
                    
             
        
        
        
Answer:
oxygen
Explanation:
oxygen is an essential nutrient which the body needs especially during respiration.
it help the blood cells do provide energy.
without oxygen, there is no gaseous exchange
 
        
                    
             
        
        
        
I believe it is scientific laws.