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
[{'content': 'Bird of prey sign is seen in \nSelect and explain. \nA. Gastric volvulus, B. Intussusception, C. Sigmoid volvulus, D. Caecal volvulus', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Sigmoid volvulus is a cause of large bowel obstruction and occurs when the sigmoid colon twists on the sigmoid mesocolon. Imaging signs areRadiograph:coffee bean signFrimann Dahl&;s sign - three dense lines converge towards the site of obstructionabsent rectal gas water-soluble contrast enema - the beak sign (or bird beak sign). CTlarge gas-filled loop without haustral markings, forming a closed-loop obstructionwhirl sign: twisting of the mesentery and mesenteric vesselsbeak sign: if rectal contrast has been administered (Ref: Grainger and Allison&;s diagnostic radiology 6th edition, chapter 25)', 'role': 'assistant'}]