<prompt> Therapeutic index of a drug is a measure of its?SafetyEfficacyPotencySelectivity  <response>: Therapeutic Index tells about the safety margin of drug; narrow therapeutic index means unsafe drug. TI : LD50ED50 LD50 : lethal dose in 50 of population.ED50 : effective dose in 50 of population or median effective dose.LD50 and ED50 can be calculated by plotting a quantal DRC. In this Quantal DRC, x-axis represents the log dose and y-axis represents the percentage of population responding. Graded dose response curve tells about the potency and efficacy of a given drug in a paicular individual. 