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: Gynaecology & Obstetrics
[{'content': 'Tamoxifen is : \nSelect and explain. \nA. Non steroidal antiprogesterone, B. Non steroidal antioestrogenic, C. Synthetic progestogen norethindrone, D. Competitive inhibitor of the 5alpha-reductase', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Non steroidal antioestrogenic', 'role': 'assistant'}]