The diagram below shows simplified schematics of two different types of circulatory systems found in multicellular animals, System X and System Y.
Which of the following statements correctly explains a physiological advantage of System Y over System X in active multicellular animals?
In System Y, blood is repressurised by the heart after passing through the gas exchange surface, allowing oxygenated blood to be delivered to respiring body tissues at a higher pressure than in System X.
In System X, oxygenated and deoxygenated blood mix within the single circuit, which reduces the concentration gradient for oxygen diffusion at respiring tissues compared to System Y.
In System Y, the blood pressure in the pulmonary circuit is higher than the blood pressure in the systemic circuit, ensuring more rapid uptake of oxygen at the alveoli.
Because System Y contains a four-chambered heart, it allows the use of hemoglobin for oxygen transport, whereas animals with System X must rely on simple diffusion in the plasma.
