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: Radiology
Hat sign on double contrast barium enema is seen in – 
Select and explain. 
A. Ulcer, B. Polyp, C. Carcinoma, D. Diverticulum
B: Polyp
Answer: B: Polyp 
Explanation: Hat sign on barium enema is seen in colonic polyp.