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: ENT
[{'content': "Muller's maneuver is - \nSelect and explain. \nA. Forceful expiration against closed glottis, B. Forceful inspiration against closed glottis, C. Forceful expiration against open glottis, D. Reverse of Valsalva maneuver", 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]