This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ear, Subject name: ENT
[{'content': 'Commonest cause of Eustachian tube disease is \nSelect and explain. \nA. Adenoids, B. Sinusitis, C. Otitis media, D. Pharyngitis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Adenoids cause eustachian tube dysfunction by a) Mechanical obstruction to tubal opening b) Acting as a reservoir for pathogenic organisms c) In case of allergy, mast cells of the adenoid tissue release inflammatory mediators which cause tubal blockage (Ref: Textbook of diseases if ENT, PL Dhingra, 7th edition, pg no. 64)', 'role': 'assistant'}]