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
Of the different epidemiological study designs available to test the association between risk factor and disease, the best design is of 
Select and explain. 
A. Case control study, B. Ecological study, C. Coho study, D. Cross sectional study
C: Coho study
Answer: C: Coho study 
Explanation: Coho study is also known as incidence study. The cohos are identified prior to the appearance of disease under investigation. The study group so defined are observed over a period of time to determine the frequency of disease among them. Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 83