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
This 23-year-old man was involved in a motor vehicle accident. What is the diagnosis? 
Select and explain. 
A. Aortic dissection, B. Cardiac rupture, C. Diaphragmatic rupture, D. Pneumothorax
D: Pneumothorax
Answer: D: Pneumothorax 
Explanation: 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 The patient's endotracheal tube needs to be withdrawn further into the trachea.