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
Incidence of diarrhoea in a community can be calculated by - 
Select and explain. 
A. Case control study, B. Cohort study, C. Cross sectional study, D. Double blind placebo control study
B: Cohort study
Answer: B: Cohort study 
Explanation: None