I think it is C, though not sure. Hope this helps you.
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 :)
It can be C or D but I think the answer is D
C<span>ondensation plays a significant role in the formation of clouds. </span>