Which of these BEST describes our current understanding about how species evolve over time?
A As organisms use certain traits more frequently, each organism evolves over time.
B Populations of organisms evolve rapidly due to genetic changes brought about by random mating patterns.
C Traits that result in a greater number of mutations occur more frequently, causing the population to evolve.
D Populations evolve as natural selection results in a change in the frequency of alleles within the population over time.