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
Thickness of lead apron to prevent radiation: 
Select and explain. 
A. 1 mm, B. 3 mm, C. 0.5 mm, D. 7 mm
C: 0.5 mm
Answer: C: 0.5 mm 
Explanation: Ans. 0.5 mm