<prompt> The floor of the fourth ventricle contains all except -Abducent nucleusFacial nucleusDorsal vagal nucleusHypoglossal nucleus  <response>: Nuclei in the floor of 4th ventricleAbducent nucleus lies below facial colliculus.Vestibular nuclei below vestibular area.Dorsal nucleus of vagus below vagal triangle and hypoglossal nucleus below the hypoglossal triangle.Option b requires some explanationThe facial nerve is present on the floor of the 4th ventricle at facial colliculus. But the facial nucleus is not present in the floor of the 4th ventricle. 