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: Pharmacology
[{'content': 'Tamoxifen is useful in: \nSelect and explain. \nA. Carcinoma prostate, B. Carcinoma ovary, C. Estrogen receptor positive breast carcinoma, D. Seminoma', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]