Which of the following is an example of heritable variation?

Heritable variation refers to differences in traits that can be passed from parents to their offspring through genes. The correct choice identifies genetic traits, which are determined by the DNA inherited from both parents. These traits can influence various characteristics, such as hair color, eye color, and susceptibility to certain diseases. Because these traits are encoded in the organism's genetic material, they can be transmitted to the next generation, allowing for the continuation of variation within a population.

The other options reflect non-heritable changes or traits. Acquired traits result from environmental influences or experiences during an individual's lifetime and cannot be passed down to offspring. Environmental adaptations may improve an organism's survival in a particular habitat, but these changes do not alter the genetic code and therefore are not heritable in the genetic sense. Mutations in somatic cells affect only the individual organism and do not contribute to heritable variation since they do not occur in the germ cells responsible for reproduction.