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: Gynaecology & Obstetrics
Anti D immunoglobulin must be given to a mother of 0 negative group with a bay of 0 positive within: 
Select and explain. 
A. At bih 4 hours, B. 4 hours, C. 24 hours, D. 72 hours
D: 72 hours
Answer: D: 72 hours 
Explanation: 72 hours