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
Demographers are of the view that the demographic goal of NRR=1 can be achieved only if the couple protection rate exceeds - 
Select and explain. 
A. 40%, B. 50%, C. 60%, D. 70%
C: 60%
Answer: C: 60% 
Explanation: None