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': "Not  a Tests for Eustachian Tube \nSelect and explain. \nA. Glycerol Test, B. Valsalva Maneuver, C. Frenzel test, D. Tonybee's test", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]