You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Which of the following statement is true - and explain in detail?
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).