This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Non communicable diseases, Subject name: Social & Preventive Medicine
Child survival index is the percentage of children surviving till the age of - 
Select and explain. 
A. 1 year, B. 3 years, C. 5 years, D. 15 years
C: 5 years
Answer: C: 5 years 
Explanation: park's textbook of preventive and social medicine 23rd edition. *child survival index:the basic measurement of infant and child survival is the under 5 moality.A child survival rate per 1000 bih can be simply calculated by subtracting the under 5 moality rate from 1000 dividing this figures by 10 shows the percentage of those who survive to the age of 5 year.