This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Rectum, Subject name: Surgery
[{'content': 'Plain abdominal X-ray is useful in: \nSelect and explain. \nA. Acute pancreatitis, B. Cholesterol stones, C. Ca cecum, D. Sigmoid volvulus', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. (d) Sigmoid Volvulus* Sigmoid Volvulus shows Coffee bean appearance in X-ray* Sigmoid Volvulus Shows Bird beak appearance in Barium enema', 'role': 'assistant'}]