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
Commonest cause of Eustachian tube diseases - 
Select and explain. 
A. Adenoids, B. Sinusitis, C. Otitis media, D. Pharyngitis
A: Adenoids
Answer: A: Adenoids 
Explanation: None