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': 'Volume of lung after maximal forceful expiration ? \nSelect and explain. \nA. Tidal volume, B. Residual volume, C. Inspiratory reserve volume, D. Expiratory reserve volume', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Residual volume", 'role': 'assistant'}]