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: Unknown
[{'content': 'All of the following from the floor of the third ventricle, Except- \nSelect and explain. \nA. Infundibulum, B. Oculomotor nerve, C. Mammillary body, D. Optic chiasma', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans-B', 'role': 'assistant'}]