<prompt> The most common source of pulmonary embolism is:Amniotic fluid embolismCalf vein thrombiLarge veins of legCardio thoracic surgery  <response>: Answer is C Large veins of leg: About half the patients with pelvic vein thrombosis or proximal leg deep vein thrombosis have pulmonary thromboembolism. Isolated calf vein thrombosis pose a lower risk of pulmonary embolism- Harrisons 