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
Zero dose of Polio vaccine in which is given: 
Select and explain. 
A. Before giving DPT, B. At bih, C. When child is having diarrhoea, D. When child is having polio
B: At bih
Answer: B: At bih 
Explanation: At bih