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
Natural history of disease can be studied by ? 
Select and explain. 
A. Cross sectional study, B. Ecological study, C. Coho study, D. RCT
C: Coho study
Answer: C: Coho study 
Explanation: Ans. is 'c' i.e., Coho study Longitudinal studies are used to study natural history of disease. Among the given options, only coho study is a longitudinal study.