Answer:
D) a population's allele frequencies change over a span of generations.
Step-by-step explanation:
Microevolution occurs within a population whereby gene flow, mutation, genetic drift or natural section brings about a change in a population’s allele frequencies over several generations. It occurs on a small scale. Examples of microevolution can be observed in resistance being evolved by pests to pesticides. i.e. Mosquitoes developing resistance against DDT. Mosquitoes with genes that can withstand DDT have evolved overtime.