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
[{'content': 'Demographers are of the view that the demographic goal of NRR=1 can be achieved only if the couple protection rate exceeds - \nSelect and explain. \nA. 40%, B. 50%, C. 60%, D. 70%', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]