Preference of epidemiological studies for establishing causality:-: (A) RCT > Retrospective coho > Prospective coho > Case control > Cross sectional, (B) RCT > Prospective coho > Retrospective coho > Case control > Cross sectional, (C) RCT > Prospective coho >Retrospective coho > Cross sectional > Case control, (D) RCT > Retrospective coho > Prospective coho > Cross sectional > Case control
Answer is A. Preference of epidemiological studies for establishing causality:- Double blind RCT > Retrospective coho > Prospective coho > Case control > cross sectional > Ecological study.