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': 'Walls of the CT scanner room are coated with – \nSelect and explain. \nA. Lead, B. Glass, C. Tungsten, D. Iron', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Lead is the most common agent used in modern constructions (Room design) to offer radiation shielding.', 'role': 'assistant'}]