Natural selection occurs when individuals with certain genotypes are more likely than individuals with other genotypes to survive and reproduce, and thus to pass on their alleles to the next generation. As Charles Darwin (1859) argued in "On the Origin of Species", if the following conditions are met, natural selection must occur:1) There is variation among individuals within a population in some trait.2) This variation is heritable (i.e., there is a genetic basis to the variation, such that offspring tend to resemble their parents in this trait).3) Variation in this trait is associated with variation in fitness (the average net reproduction of individuals with a given genotype relative to that of individuals with other genotypes).Hence option D is correct.If the environmental conditions are stable or if there is a stable population of predators, then there will be no selection pressure. Therefore option A, B and C are incorrect.