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': 'Most common cause of pyometra is : \nSelect and explain. \nA. Senile endometriosis, B. Carcinoma endometrium, C. Carcinoma cervix, D. Carcinoma ovary', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Carcinoma endometrium', 'role': 'assistant'}]