Two tubes are inoculated from one test tube of a bacterial culture. The cultures are then transferred every day for 2 months. All of the media and growth conditions are the same in every tube. After 2 months of cultivation, the fitness and genotype frequencies of the populations in the two tubes are compared. The fitness of the two cultures is the same, but the genotype frequencies are very different in the two cultures. How is this possible? A) Two months is not long enough for different fitness levels to evolve even if the genotype frequencies change. B) This result is not possible because different genotype frequencies would result in different fitness levels under the same growth conditions. C) Natural selection caused the evolution of different genotype frequencies within the separate test tubes. D) Genetic drift within the small populations in the test tubes resulted in different genotype frequencies.