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': 'True statement regarding pulmonary ventilation is - \nSelect and explain. \nA. PaO2 is maximum at the apex, B. V/Q is maximum at the base, C. Ventilation per unit lung volume is maximum at the apex, D. Blood circulation is minimum at the base', '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 and the PaO2 is maximum at the apex. PCO2 is maximum at the base.', 'role': 'assistant'}]