question: Q:A 7-year-old girl is brought to the physician because of vaginal bleeding for 2 days. There is no personal or family history of serious illness. She is at the 95th percentile for height and at the 90th percentile for weight. Examination shows enlarged breasts, and the areola and papilla have formed a secondary mound. There is coarse pubic hair that does not extend to the inner thigh. The remainder of the examination show no abnormalities. An x-ray of the left hand and wrist shows a bone age of 11 years. Her serum luteinizing hormone concentration is 0.1 mIU/mL (N < 0.2 mIU/mL). Which of the following is the most appropriate next step in management?? 
  {'A': 'MRI of the brain', 'B': 'Ultrasound of the pelvis', 'C': 'Reassurance and follow-up', 'D': 'GnRH stimulation test', 'E': 'Serum dehydroepiandrosterone level'},