This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thromboembolism and Fat Embolism Syndrome, Subject name: Medicine
A 52-year-old businessman with nephrotic syndrome after a non-stop flight from New York to New Delhi presents with sudden onset of breathlessness, haemoptysis, and chest pain. He is brought into Casualty in shock. His chest X-ray is normal. The ECG shows sinus tachycardia. 
Select and explain. 
A. Pneumothorax, B. Myocardial infarction, C. Pulmonary embolism, D. Aoic dissection
C: Pulmonary embolism
Answer: C: Pulmonary embolism 
Explanation: 1. In this patient no pulmonary edema, MI absent and aoic dissection also absent. 2. Nephrotic syndrome patient will be in hypercoagulable state, long flight- DVT- pulmonary embolism- acute Cor pulmonale 3. Most common causes of Cor pulmonale- pulmonary embolism 4. CXR is normal because it is only a small clot and clot usually not visible on X-ray