This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Physiology
[{'content': 'Ventilation perfusion ratio is maximum at \nSelect and explain. \nA. Posterior lobe of lung, B. Middle lobe, C. Apex of lung, D. Base of lung', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ventilation perfusion ratio is maximum at the apex of the lung Ref: guyton and hall textbook of medical physiology 12 edition page number: 332,333,334', 'role': 'assistant'}]