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: Anaesthesia
[{'content': 'Which of the following is not reduced in elderly patient \nSelect and explain. \nA. Functional residual capacity, B. Arterial oxygen tension, C. Alveolar oxygen tension, D. Forced expiratory volume', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Functional residual capacity is unchanged in elderly patients. Closing capacity falls progressively with age.', 'role': 'assistant'}]