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': 'In upper airway obstruction all of the following changes are seen except \nSelect and explain. \nA. Decreased maximum breathing capacity, B. RV decreased, C. Decreased FEV, D. Decreased Vital capacity', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b) RV decreased(Ref: Ganong, 25th ed/p.628)Increase in residual volume denotes "air trapping" which is classically seen in obstructive lung diseases', 'role': 'assistant'}]