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': 'Failure of bleeding after withdrawal of oestrogen indicates : \nSelect and explain. \nA. Uterine factor, B. Ovarian factors, C. Pituitary factor, D. Hypothalamic factor', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Uterine factor', 'role': 'assistant'}]