The correct option is D Survival of the fittest
“Survival of the fittest” is a popular term that refers to the process of natural selection, a mechanism that drives evolutionary change. Natural selection works by giving individuals who are better adapted to a given set of environmental conditions, an advantage over those that are not as well adapted.
The concept of the struggle for existence concerns the competition or battle for resources needed to live.
Differential reproduction is a variation in the amount of offspring produced by individuals in a population.
Sexual selection is a mode to choose sex partner of an organism to mate.