The Blood Leaving The Tissues Becomes Richer in (a) Carbon Dioxide (b) Water (c) Haemoglobin (d) Oxygen

Answer: (a) Carbon dioxide

Because oxygen was taken into the body at the lungs, the blood that travels through the body to the tissues is rich in oxygen and nutrients. However, as the blood is leaving the tissues, its concentration of carbon dioxide and urea increases. This is because carbon dioxide and urea are metabolic wastes that are produced by the cells of the tissue and are collected by the blood. The alveoli in the lungs are responsible for the diffusion of carbon dioxide, whereas the kidneys are responsible for the filtration of urea and the subsequent excretion of urine.