This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'In comparison to the apex of the lung, the base of the lung has \nSelect and explain. \nA. High pulmonary arterial pressure O2, B. High pulmonary arterial pressure CO2, C. High ventilation / perfusion ratio, D. Same ventilation / perfusion ratio', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Apical alveoli have low ventilation and perfusion per unit volume of the lung, whereas the basal alveoli have high ventilation and perfusion.\nVentilation-perfusion ratio and the PaO2\xa0is maximum at the apex. PCO2\xa0is maximum at the base.', 'role': 'assistant'}]