Darwin’s theory of natural selection is often referred to as survival of the fittest. which statement most accurately reflects "fitness" according to darwin’s natural selection? explain how you got your answer.

a. fitness is the measure of an individual organism's adaptability to various habitats in an environment.

b. fitness reflects the ability of an organism to run faster and hide better or to hunt and kill more efficiently.

c. fitness refers to the relative health of each individual in the population so they could survive diseases.

d. fitness is an individual organism’s reproductive success in surviving and producing viable offspring.