This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Medicine
[{'content': 'Pulmonary embolism is most commonly produced by which of the following \nSelect and explain. \nA. Trauma, B. Atherosclerosis, C. Thrombosis of pelvic vessels, D. None', 'role': 'user'}, {'content': "Answer: C \nExplanation: When venous thrombi are dislodged from their site of formation,they embolize to the pulmonary aerial circulation producing pulmonary embolism.About one-half of patients with pelvic vein thrombosis develop pulmonary embolism.Other causes of pulmonary embolism include hip/knee surgery,trauma,pregnancy,immobility,thrombotic disorders. Reference:Harrison's medicine-18th edition,page no:2171;Davidson's medicine,22nd edition,page no:721.", 'role': 'assistant'}]