Final answer:
The statement that individuals best suited to their environment survive and reproduce most successfully, according to Darwin, is true. This reflects the fundamental concept of natural selection, where traits beneficial for survival tend to become more prevalent in a population over generations.
Step-by-step explanation:
This concept is a central pillar of Darwin's theory of evolution, known as natural selection. For example, if a selective pressure such as a predator exists in an environment, individuals that can avoid predation effectively, due to traits like better speed or better camouflage, are more likely to survive. Over time, these advantageous traits become more common in the population because the individuals with them tend to have more offspring that inherit those traits. Thus, natural selection leads to a population that is better adapted to its environment.