Breathing and Heart rate cause oxygenated blood to be delivered to all tissues around the body. plz mark mine as brainiest plz cuz I need help on ranking up even check my profile plz much appreciated if done plz plz plz thxplz mark mine as brainiest plz cuz I need help on ranking up even check my profile plz much appreciated if done plz plz plz thx
 
        
        
        
It could be a yes or no... to me because you try something you did try an put your work in to it when it was hard work.... I agree because you always try when you do something... if it can't be proven at least you tried on it
        
             
        
        
        
I’m pretty sure it’s the first option, if not I am so sorry.
        
                    
             
        
        
        
D. He controlled variables by studying one or two traits at a time