Case fatality rate is -

Ans. is 'b' i.e., Killing power of disease * CFR represents the killing power (severity) of a disease.CFR=Total no. of deaths due to a disease--------------------------------Total no. of cases of the same diseasex 100* CFR is typically used in acute infectious disease e.g.food poisoning, cholera, measles. Its usefulness in chronic disease is limited, because the period from onset to death is long and variable.* CFR is closely related to virulence of agent.* Limitation of CFR is that time period is not specified.* The case fatality rate for the same disease may vary in different epidemics because of changes in host, agent and environment factors.