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': 'An alternate to lead in the walls of radiology room is: \nSelect and explain. \nA. Walls made up of 3 inch concrete, B. Walls made up of barium plaster or barium concrete, C. Walls made up of 3 inch steel, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Walls made of 3" concrete, 3" x\xa016" of steel or 1 mm of lead, barium plaster or barium concrete will suffice to protect adjacent rooms from radiation.', 'role': 'assistant'}]