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': 'Which nucleus is not found in the floor of the fouh ventricle \nSelect and explain. \nA. Abducens N, B. Dorsal vagal nuclei, C. Dorsal vagal nuclei, D. None', 'role': 'user'}, {'content': 'Answer: D \nExplanation: D i.e., None', 'role': 'assistant'}]