The two facts from Parts C and D lead to the "inescapable conclusion" that individuals in a population will have unequal reproductive success, so that those whose traits best enable them to survive will leave more offspring. Therefore, in any local environment, over time, .

Heritable traits that enhance survival will become progressively more common in succeeding generations.

Explanation:

Charles Darwin's theory of evolution developed many ideas; among them we find the "Adaptation", which describes just what the exercise explains: the "inescapable conclusion" that individuals in a population will have unequal reproductive success, so that those whose traits best enable them to survive will leave more offspring. In other words, among a species, the individuals who have the best heritable traits will be able to have more offspring, and, therefore, those traits will be more and more common in the following generations.