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: Unknown
[{'content': 'Halban disease is due to \nSelect and explain. \nA. Persistent corpus luteum, B. Deficient corpus luteum, C. Persistent trophoblast, D. Deficient trophoblast', 'role': 'user'}, {'content': "Answer: A \nExplanation: Irregular shedding (Halban's disease)\nIt is rare and self-limited. It is due to persistent corpusluteum. The menstruation comes on time, is prolonged but not heavy. Progestogen can suppress the bleeding, but needs to be taken on tapering dose for 20 days to complete the cycle.", 'role': 'assistant'}]