Answer:
D variations in individuals are not heritable
Step-by-step explanation:
Genetic variation in individuals is what drives evolution. In a population of individuals in an environment, with the adequate resources, overpopulation can occur. However, resources are usually a limiting factor for population growth: there is not sufficient food/shelter etc. for everyone to survive.
Some individuals are better suited to success in the environment. This is because of random variation in their DNA that has arisen that give them a selective advantage. This allows them to thrive, take advantage of the limited resources over other members of the population, and be more likely to survive to reproductive age. This is natural selection.
Because this variation is genetic (in the DNA), they can then pass it on to their offspring. Over time, this leads to evolution over time.