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
Prevalance of cataract at one point of time can be determined by - 
Select and explain. 
A. Longitudinal study, B. Cross-sectional study, C. Surveillance, D. Coho study
B: Cross-sectional study
Answer: B: Cross-sectional study 
Explanation: Ans. is 'b' i.e., Cross-sectional study o This queston is straight forward, Prevelance is obtained by cross-sectional study and therefore cross-sectional study is also known as prevalence study.