This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastrointestinal Radiology, Subject name: Radiology
[{'content': 'Air under central tendon of diaphragm is \nSelect and explain. \nA. Air under diaphragm sign, B. Cupola sign, C. Doges cap sign, D. Falciform ligament sign', 'role': 'user'}, {'content': "Answer: B \nExplanation: The 'Cupola sign' is seen on a supine chest/abdominal radiograph in the presence of pneumoperitoneum. It refers to non-dependent gas that rises within the abdominal cavity of the supine patient to accumulate underneath the central tendon of the diaphragm in the midline.", 'role': 'assistant'}]