<prompt> Case control study :Is a prospective studyGives Odd ratioUseful in case of rare diseaseBoth 2 and 3  <response>: Case control:A retrospective study.Risk factor is to be identified disease present Gives Odds ratio.Best method to study RARE disease Case control study.NESTED Case-control studyIt is a case-control study nested within COHORT study. So, it is a prospective study. 