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': 'Volume of air remaining in lung after normal expiration: \nSelect and explain. \nA. Functional residual capacity, B. Residual volume, C. Vital capacity, D. Both 1and 2', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Functionality residual capacity: amount of air remaining in the lung after normal expiration. Residual volume: amount of air remaining in the lung after forced expiration. Ref : G K Pal textbook of Practical physiology 4th edition, page number: 159', 'role': 'assistant'}]