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
Eustachian tube patency seen by ? 
Select and explain. 
A. Valsalva, B. Methylene blue test, C. Tonybee test, D. All the above
D: All the above
Answer: D: All the above 
Explanation: Ans. is d i.e., All the above Tests for Eustachian tube patency Valsalva test Methylene blue test Sonotubometry Politzer test Toynbee test Frenzel maneuver Catheterization Inflation - Deflation test