This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Plain Film Radiography, Fluoroscopy, and Tomosynthesis, Subject name: Radiology
[{'content': 'Shield used in radiology are made up of? \nSelect and explain. \nA. Lead, B. Copper, C. Mercury, D. Silica', 'role': 'user'}, {'content': 'Answer: A \nExplanation: ANSWER: (A) LeadREF: Park 20th ed p. 651Effective protective measures in radiology units should include proper use of lead shields and lead rubber aprons (0.5 mm of lead) and a film badge or dosimeter.Permissible dose of radiation from man made sources: 5 rad/year', 'role': 'assistant'}]