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: Radiology
[{'content': 'Filters of which metal that is used to remove long wave\nlength X-rays from the primary beam is: \nSelect and explain. \nA. Platinum, B. Aluminium, C. Copper, D. Lead', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]