<prompt> True about vertebral artery -a Enter skull through condylar canal.b Branch of internal carotid arteryc Branch of subclavian arteryd Accompany sympathetic ganglione Passes through foramen transversarium of cervical vertebraeabdacdcdeade  <response>: Vertebral artery enters skull posterior cranial fossa through foramen magnum.Vertebral artery is a branch of subclavian artery.It is accompanied by sympathetic peri-arterial plexus, inferior cervical stellate sympathetic ganglion and ventral rami of 7th and 8th cervical spinal nerves.Vertebral artery passes through foramina transversaria of upper six cervical vertebrae. 