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: Pathology
[{'content': 'Vaginal adenocarcinomas in children is caused by- \nSelect and explain. \nA. Virus, B. Adminstration of DES to pregnant mothers, C. Hormonal changes, D. All of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Adenocarcinoma occurs in young women whose mothers had been treated with diethylstilbestrol (DES) during pregnancy.', 'role': 'assistant'}]