Ans. is 'a' i.e., VIII o The nucleus ambiguus is located just posterior to the inferior olivary nucleus in the lateral portion of the upper part of the medulla.o This nucleus gives rise to:The branchial efferent motor fibers of the vagus nerve (X nerve).Efferent motor fibers of glossopharyngeal nerve (X nerve) terminating in the stylopharyngeus muscle.A part of the cranial root of accessory nerve (XI nerve).Vertebral ArteryIt arises from a 1st part of the subclavian arteryFirst Part: Origin to the foramen transversarium of C, vertebra. It lies in the scalenovertebral/vertebral triangle (triangle of vertebral artery) between scalenus anterior and longus colli muscles.Second Part: This part passes through foramina transversaria of upper 6 cervical vertebrae (C6 to C1).Third Part: It extends from foramen transversarium of C1. to foramen magnum, lying in a groove on the upper surface of the posterior arch of the atlas. This part of the artery lies in the suboccipital triangle. It then enters the vertebral canal by passing deep to the lower arched margin of the posterior atlanto-occipital membrane.Fourth Part: It lies in the posterior cranial fossa extending from the foramen magnum to the lower border of the pons.In the vertebral canal, it pierces the dura and arachnid and ascends in front of hypoglossal nerve roots. At the lowerthe border of pons both vertebral arteries unite to form the basilar artery.Cervical branchesSpinal branches: Enter vertebral canal through intervertebral foramina and supply cervical segments of spinal cord, meninges, and vertebrae.Muscular branches : Supply suboccipital muscles.Cranial Branches :Meningeal: Supply meninges of posterior cranial fossaPosterior spinalAnterior spinalMedullaryPosterior inferior cerebellarBasilar artery: A single median vessel formed by the union of the two vertebral arteries at the lower border of the pons, runs upward in front of the pons, embedded in the groove, to bifurcate into two posterior cerebral arteries at the upper border of the pons. Its branches are :Labyrinthineanterior inferior cerebellarPontineSuperior cerebellarPosterior cerebral