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: Dental
The threshold limit value of mercury exposures is: 
Select and explain. 
A. 0.01 mg / m3, B. 0.05 mg/ m3, C. 0.1 mg /m3, D. 0.001 mg /m3
B: 0.05 mg/ m3
Answer: B: 0.05 mg/ m3 
Explanation: None