This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
[{'content': 'The floor of the fourth ventricle contains all except - \nSelect and explain. \nA. Abducent nucleus, B. Facial nucleus, C. Dorsal vagal nucleus, D. Hypoglossal nucleus', 'role': 'user'}, {'content': "Answer: B \nExplanation: Nuclei in the floor of 4th ventricle\n\nAbducent nucleus lies below facial colliculus.\nVestibular nuclei below vestibular area.\nDorsal nucleus of vagus below vagal triangle and hypoglossal nucleus below the hypoglossal triangle.\n\nOption 'b' requires some explanation\n\nThe 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.", 'role': 'assistant'}]