Answer:
B. CO2 out
Explanation:
The excretion is the process of removal of the waste product from the body. The carbon dioxide is the byproduct of the aerobic respiration, which is carries from the tissues and the lungs by blood. In the lungs at alveoli, the carbon dioxide is transferred from the blood to the lungs and released out through the nostrils. Hence, the out of the carbon dioxide represent excretion through lungs.
