This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
Autosomal recessive disease have incidence of 1/ 250000 in a population. What is the carrier state of population? 
Select and explain. 
A. 1\/250, B. 1\/500, C. 1\/1000, D. 1\/5000
A: 1\/250
Answer: A: 1\/250 
Explanation: .incidence is calculated as the total number new cases in a given time period divided by population at risk during that period.multiplied by 1000.so here total no of carrier states is given by 1divided by 250000 multiplied by 1000,that is 1/250. ref:park&;s textbook,ed 22,pg no 58