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: Unknown
[{'content': '20-years-old male with history of RTA presents with breathlessness.  Stratosphere sign on USG with M mode is seen.  What is the probable diagnosis? \nSelect and explain. \nA. Hemothorax, B. Pneumothorax, C. Cardiac tamponade, D. Pulmonary embolism', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Radiological signs in trauma (eFAST)', 'role': 'assistant'}]