This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': 'A 51 yr female with ductal ca in situ of breast is best managed by: \nSelect and explain. \nA. Breast conservative surgery, B. Simple mastectomy, C. Modified radical mastectomy, D. Radical mastectomy', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]