Answer: The Pulmonary vein blood vessel carries oxygenated blood from the lungs back to the heart. Therefore, it carries the highest concentration of oxygen.
Explanation: i think is the answer not sure hope it help this question :)
 
        
             
        
        
        
Answer:
the answer is neutrophils 
 
        
             
        
        
        
I wpupd say D but im not sure