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: None