<prompt> The most malignant brain tumour isEpendymomaMedulloblastomaOligodendrogliomaGlioblastoma multiforme  <response>: D Glioblastoma multiforme Glioblastoma multiforme GBM, WHO classification name glioblastoma, also known as Grade IV Astrocytoma, is the most common and most aggressive malignant primary brain tumor in humans, involving glial cells and accounting for 52 of all functional tissue brain tumor cases and 20 of all intracranial tumors. 