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
Which of the following is not reduced in elderly patient 
Select and explain. 
A. Functional residual capacity, B. Arterial oxygen tension, C. Alveolar oxygen tension, D. Forced expiratory volume
A: Functional residual capacity
Answer: A: Functional residual capacity 
Explanation: Functional residual capacity is unchanged in elderly patients. Closing capacity falls progressively with age.