This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Physiology
"Air crescent" sign is seen in 
Select and explain. 
A. Hydatid cyst, B. Aspergillosis, C. Tuberculosis cavity, D. Amoebic liver abscess
B: Aspergillosis
Answer: B: Aspergillosis 
Explanation: "Air crescent" sign is seen in fungal ball or aspergilloma in a tubercular cavity. Ref ganong's review of medical physiology 25e 765