This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Breast Cancer - Treatments, Subject name: Surgery
[{'content': 'Sentinel lymph node biopsy in carcinoma breast is done if - \nSelect and explain. \nA. LN palpable, B. Breast mass but no lymph node palpable, C. Breast lump with palpable axillary node, D. Metastatic CA breast', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Breast mass but no lymph node palpable", 'role': 'assistant'}]