Answer:
i would think its the nervous system
Explanation:
 
        
                    
             
        
        
        
That would be A and E. 
because u can measure or calculate the variables in these 2 hypotheses. (Amount of protein is diet, muscle mass, salt intake, blood pressure.)
        
                    
             
        
        
        
Carbohydrate is a carb found in your diet of foods that provides glucose which is the basic form of energy and also carbohydrates are one of your macronutrients