A farmer sprays insecticide on his crops to kill unwanted insects. Most of the insects die, and the chemicals have the effect of damaging the DNA of the insects that are not killed. Which of these has happened? A. Sexual selection among the insects has changed the gene pool. B. Genetic equilibrium has been maintained. C. Mutations have arisen that may have altered allele frequencies. D. Individuals with new genes have immigrated into the population.