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
Cause of U/L secretory otitis media in an adult is - 
Select and explain. 
A. CSOM, B. Nasopharyngeal carcinoma, C. Mastoiditis, D. Foreign body of external ear
B: Nasopharyngeal carcinoma
Answer: B: Nasopharyngeal carcinoma 
Explanation: Unilateral serous otitis media in an adult should always raise the suspicion of a benign / malignant tumor of nasopharynx
“In adults presenting with a unilateral middle ear effusion the possibility of a nasopharyngeal carcinoma should be considered”.
Ref. Dhingra 5/e, p 72, 6/e, p 251; Current Laryngology 2/e, p 659