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': 'Risk factors of pulm embolism \nSelect and explain. \nA. 30 yrs female of OCPs, B. Pregnancy, C. Leg paralysis, D. All', 'role': 'user'}, {'content': "Answer: D \nExplanation: Risk factors for pulmonary embolism include (a) Surgical-major abdominal/pelvic surgery,hip/knee surgery,post operative intensive care; (b) Obstetric-pregnancy/puerperium,use of OCPs; (c) Cardiorespiratory-COPD,congestive cardiac failure; (d) Lower limb problems-fracture,varicose bins,stroke/spinal cord injury; (e) Malignant-abdominal/pelvic,advanced/metastatic,concurrent chemotherapy; (f) Miscellaneous- increasing age,immobility,thrombotic disorders,trauma. Reference:Davidson's medicine-22nd edition,page no:721.", 'role': 'assistant'}]