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
Recommended dose of anti-rabies serum to be given for passive immunization of adult victim of dog bite is 
Select and explain. 
A. 20 i.u., B. 40 i.u., C. 60 i.u, D. 80 i.u.
A: 20 i.u.
Answer: A: 20 i.u. 
Explanation: None