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
Calculate the prevalence if incidence is 2 cases per 1000 population oer year and mean duration is 4 years - 
Select and explain. 
A. 8 cases per 1000 population, B. 2 cases per 1000 population, C. 0.5 cases per 1000 population, D. 32 cases per 1000 population
A: 8 cases per 1000 population
Answer: A: 8 cases per 1000 population 
Explanation: the relationship between incidence and prevalence can be calculated as,prevalence =incidence*mean duration ,here in this case it equals 2*4 that is 8 cases per 1000 population. ref:park&;s textbook of preventive and social medicine,22nd edition,pg no 58