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
In a population of 5000, incidence of disease is 100 in 1 year duration of disease studied for is 2 years calculate Prevalance - 
Select and explain. 
A. 20/1000, B. 40/1000, C. 80/1000, D. 400/1000
B: 40/1000
Answer: B: 40/1000 
Explanation: Ans. is 'b' i.e., 40/1000