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 is 
Select and explain. 
A. 0.25 mm, B. 0.3 mm, C. 0.4 mm, D. 0.5 mm
D: 0.5 mm
Answer: D: 0.5 mm 
Explanation: Thickness of lead apron is 0.5 mm.