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
Blue ear drum is seen in - 
Select and explain. 
A. Serous otitis media, B. CSOM, C. Perforation, D. None
A: Serous otitis media
Answer: A: Serous otitis media 
Explanation: None