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': 'Which of the following is true about ventilation and perfusion in alveoli in an erect posture \nSelect and explain. \nA. Ventilation/perfusion ratio is maximum at apex, B. Ventilation/perfusion ratio is maximum at base, C. Ventilation is maximum at apex, D. Perfusion is maximum at apex', 'role': 'user'}, {'content': 'Answer: A \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\xa0and the PaO2\xa0is maximum at the apex. PCO2\xa0is maximum at the base.', 'role': 'assistant'}]