<prompt> Best study is -Case-control studyCohort studyMeta-analysisRCT  <response>: Ans-C Meta-analysiso Here are the different epidemiological studies with decreasing order of accuracy to test the association between risk factor and disease : -1. Systematic review and meta-analysis -- Overall most reliable2. Randomized controlled trials controlled clinical trails - Most reliable individual study.3. Retrospective Non-concurrenthistoric Cohort study.4. Prospective concurrent Cohort study.5. Case control study6. Cross-sectional study7. Ecological study 