Variations in Populations Practice Test

A population of insects has variation in a detoxification enzyme due to alleles D and d. In fields treated with a new pesticide, insects with genotype DD survive at higher rates than dd insects, and D allele frequency increases from 0.30 to 0.55 over several generations. Which statement best explains how genetic variation contributed to this evolutionary response?

In a population of field mice, fur color is controlled by two alleles. Before a wildfire, 52% of mice are light brown (genotypes BB or Bb) and 48% are dark brown (bb). After the wildfire, the habitat is mostly blackened soil. Over the next 6 generations, surveys show dark-brown mice increase to 76% while total population size remains similar. No new alleles are detected, and mating remains random within the population. Which statement best explains the observed change in the population over generations?