This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gallbladder, Subject name: Surgery
[{'content': 'Mercedes Benz sign or Seagull sign is seen in: \nSelect and explain. \nA. Gallstones, B. Renal stones, C. CBD stones, D. Hydatid cyst', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Mercedes Benz sign or Seagull sign The centre of Gallstone may contain radiolucent gas in a triradiate or biradiate fissure, this gives rise to characteristic darkshapes on radiograph- the Mercedes Benz sign or Seagull sign.', 'role': 'assistant'}]