<prompt> The most common source of pulmonary embolism is :Amniotic fluid embolismRenal artery embolismLarge veins of legCardio thoracic surgery  <response>: Ans. is c large veins of leg Ref Harrison, 17e, p 1651 16e, p 1561 15e, p. 1509.Remember thatMC site for deep vein thrombosis - Calf vein.But MC source for pulmonary emboli - Proximal vein of lower extremity femoral vein. 