This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urethra & Penis, Subject name: Surgery
[{'content': 'A 20-year-old female complains of vaginal bleeding. Diagnostic workup reveals clear cell adenocarcinoma of the vagina. A maternal history should be obtained for use of? \nSelect and explain. \nA. Thalidomide, B. Oral DES, C. Loss of sensation in the scrotum, D. absent bulbocavernosus refl', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Oral DES was given to patients who were unable to conceive. Fortunately, this complication is unlikely to occur, because DES has been withdrawn as a drug used for this purpose.', 'role': 'assistant'}]