challenge: What are the five subtypes of central nervous system primitive neuroectodermal tumors classified by the World Health Organization?
  
  A. Choroid plexus tumor, Pineal gland tumor, Pituitary gland tumor, Craniopharyngioma, Hemangioblastoma
  B. Neuroblastoma, Ganglioneuroblastoma, Medulloepithelioma, Ependymoblastoma, Not otherwise specified PNET
  C. Astrocytoma, Oligodendroglioma, Ependymoma, Medulloblastoma, Glioblastoma
  D. Meningioma, Schwannoma, Neurofibroma, Glioma, Sarcoma
  Answer: 