This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Gynaecology & Obstetrics
[{'content': 'First line of Rx of osteoporosis in postmenopausal women \nSelect and explain. \nA. Estrogen, B. Bisphosphonates, C. Raloxifene, D. Ullipsistal', 'role': 'user'}, {'content': 'Answer: B \nExplanation: REF : SHAW GYNECOLOGY REF REF :', 'role': 'assistant'}]