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: Medicine
[{'content': "A 45-year-old man presents with a history of frequent falls. He has difficulty in looking down also. What is the most probable diagnosis - \nSelect and explain. \nA. Normal pressure hydro-cephalus, B. Parkinson's disease, C. Alzheimer's disease, D. Progressive supranuclear palsy", 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]