<prompt> 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?An immature teratomaA dysgerminomaAn ovarian fibromaA mature cystic teratoma  <response>: Well-formed teeth are commonly seen in mature cystic teratoma and not in any of the other lesions. 