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': 'A 25 year old female presents with a lower abdominal mass which shows a well-formed tooth on plain x-ray. The lesion is most likely to be which of the following? \nSelect and explain. \nA. An immature teratoma, B. A dysgerminoma, C. An ovarian fibroma, D. A mature cystic teratoma', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Well-formed teeth are commonly seen in mature cystic teratoma and not in any of the other lesions.', 'role': 'assistant'}]