Following blunt chest trauma, a 35-year-old male is orally intubated and continuous mechanical ventilation is initiated. Physical assessment of the neck and chest reveal a midline trachea and significant reduction in thoracic expansion of the left chest. There are diminished breath sounds in the left lung compared to the right lung. These findings most likely indicate which of the following?

A. flail chest on right thorax
B. right tension pneumothorax
C. endobronchial intubation
D. subcutaneous emphysema

Answer: C. endobronchial intubation