Concept:The principle of “survival of the fittest” is central to Darwin’s theory of natural selection. It describes how organisms best adapted to their environment survive and reproduce.Explanation:Charles Darwin proposed the theory of evolution by natural selection in his book “The Origin of Species”. In this theory, individuals with advantageous traits are more likely to survive in the struggle for existence. These fit individuals pass on their traits to the next generation, leading to evolution. The phrase “survival of the fittest” was actually coined by Herbert Spencer after reading Darwin’s work, but the core idea belongs to Darwin. Lamarck gave the theory of use and disuse of organs, while McDougall proposed instinct theory. Harrison is not associated with this principle.Answer:The correct option is C. Darwin.