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
Mastoid reservoir phenomenon is positive in - 
Select and explain. 
A. CSOM, B. Petrositis, C. Coalescent otitis media, D. Coalescent mastoiditis
D: Coalescent mastoiditis
Answer: D: Coalescent mastoiditis 
Explanation: Mastoid reserve phenomenon is filling up of meatus with pus immediately after cleaning. It is seen in mastoiditis.
Ref. SK De, p 107, 98