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: Dental
What we will define it "ratio of no. of death under 1 year of age to total live birth per 1000 live births per year"? 
Select and explain. 
A. Infant mortality rate, B. Child mortality rate, C. Child morbidity rate, D. Life expectancy rate
A: Infant mortality rate
Answer: A: Infant mortality rate 
Explanation: None