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: Social & Preventive Medicine
Tuberculin unit is: 
Select and explain. 
A. 0.0001 mg, B. 1 unit of PPD 3, C. 0.1 mg BCG, D. None of the above
B: 1 unit of PPD 3
Answer: B: 1 unit of PPD 3 
Explanation: 1 unit of PPD 3