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: Radiology
Trapped air sign in upper abdomen on plain xray is seen in 
Select and explain. 
A. Splenic tumour, B. Renal stones, C. Pancreatitis, D. Chronic duodenal ulcer
D: Chronic duodenal ulcer
Answer: D: Chronic duodenal ulcer 
Explanation: Shopfner described this sign in patients with peri Gastric adhesions.It consists of trapped air pockets in pas of the Gastric antrum, elevated and fixed by perigastric adhesions to adjacent organs like liver and pancreasValuable in excluding Gastric carcinomasMost commonly seen in benign conditions