Ans: C. Odds ratio/Relative riskThe strength of association between the risk factor and disease is measured by the Odds ratio/Relative risk.The estimation of disease risk associated with exposure is obtained by an index known as relative risk (RR) or risk ratio, which is defined as the ratio between the incidence of disease among exposed persons and incidence among non-exposed.Odds ratio (Cross product ratio):From a case-control study, we can derive what is known as the odds ratio (OR) which is a measure of the strength of the association between risk factor and outcome.Odds ratio is closely related to relative risk.