Darwin's theories often emphasize natural selection and adaptation. Therefore, the theory that sounds most like an explanation that Darwin might give is:

"In a certain environment, individuals with advantageous traits are more likely to survive, reproduce, and pass those traits on to their offspring, leading to gradual changes in the population over time."

This explanation aligns with Darwin's theory of natural selection and explains how beneficial traits become more prevalent within a population based on their adaptive advantages in a specific environment.