Answer:
External respiration: CO2 diffuses into the blood
Explanation:
External respiration is also called the pulmonary gas exchange. It refers to the diffusion of O2 from the air in the alveoli of the lungs to blood in pulmonary capillaries and diffusion of CO2 in the opposite direction from the capillary blood into the alveolar air. External respiration in the lungs is responsible for oxygenation of deoxygenated blood coming from the right side of the heart. The oxygenated blood is then returned to the left side of the heart.
I believe that the answer is E
The temperature of the blocks is the dependent variable because it depends on the color of each block. (The black would probably be the hottest)