This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neuro-ophthalmology, Subject name: Ophthalmology
[{'content': 'Down-beat nystagmus is seen in lesion of - \nSelect and explain. \nA. Brainstem, B. Cerebellum, C. Basal ganglia, D. Hippocampus', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ref khurana 6/e p250', 'role': 'assistant'}]