This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S., Subject name: Medicine
[{'content': 'This 23-year-old man was involved in a motor vehicle accident. What is the diagnosis? \nSelect and explain. \nA. Aortic dissection, B. Cardiac rupture, C. Diaphragmatic rupture, D. Pneumothorax', 'role': 'user'}, {'content': "Answer: D \nExplanation: Answer D. PneumothoraxThe presence of a deep, lucent, right costophrenic angle on supine chest radiography is an indirect sign of a pneumothorax. In addition, a pneumothorax with associated rib fractures and subcutaneous emphysema is evident in the right chest. The patient's endotracheal tube needs to be withdrawn further into the trachea.", 'role': 'assistant'}]