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
Which of the following statement is true - 
Select and explain. 
A. Case control study is not suitable for rare diseases, B. Cohort study involves large number of subjects, C. Case-control study is relatively expensive, D. Cohort study yields relatively quick results
B: Cohort study involves large number of subjects
Answer: B: Cohort study involves large number of subjects 
Explanation: Ans. is 'b' i.e., Cohort study involves large number of subjects* Prevalence of blindness in India: 700 per 1 lakh population (0.7%) if cut of criteria is < 3/60 (WHO criteria); or 1100 per lakh population (1.1%) if cut of criteria is < 6/60 (NPCB criteria).