A 25-year-old man with asthma comes to the emergency department 30 minutes after the onset of severe shortness of breath and left-sided chest discomfort while cross-country skiing. He has no history of similar symptoms. His pulse is 110/min, respirations are 30/min, and blood pressure is 130/70 mm Hg. On auscultation, wheezes are heard that are more prominent on the right side than on the left. A chest x-ray is shown. Which of the following conditions is the most likely cause of this patient's acute dyspnea?

- AAsthma
- BMyocardial ischemia
- CPleural effusion
- DPneumothorax
- EPulmonary infarction
- FPulmonary embolism
















