This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Radiology Q Bank, Subject name: Radiology
A patient presented with a history of blunt trauma to the chest and abdomen. On USG examination in M mode the following finding is seen. What could be the likely diagnosis? 
Select and explain. 
A. Pleural effusion, B. Bronchial obstruction, C. Lung abscess, D. Pneumothorax
D: Pneumothorax
Answer: D: Pneumothorax 
Explanation: Pneumothoraxis a serious potential consequence of blunt thoracic trauma and, if misdiagnosed, it may quickly become life-threatening. On M mode of USG, classical signs for the gray scale imaging are seen: seashore sign: normal lung sliding barcode/stratosphere sign: pneumothorax