Hint: The theory of Neo-Darwinism is generally used to describe any integration of Charles Darwin’s theory of evolution by natural selection with Gregor Mendel’s theory of genetics.
Complete answer: According to Neo-Darwinism, evolution occurs by natural selection of genetically modified characters or genotypes. According to Neo-Darwinism, the formation of new species is by the accumulation of inherited random mutations and also by genetic recombination occurring due to independent assortment of crossing over during the process of fertilization. Accumulation of adaptive variation in the gene pool makes the organism better for survival to the existing environmental character. So, according to the theory of Neo-Darwinism, mutations together with natural selection are responsible for the origin of new species. Natural selection refers to the differential survival of organisms that is best suited to the environment due to the change in the genetic makeup of organisms. According to Darwin survival of the fittest was used for the organisms which were fittest in reproduction. The organism which produces more offspring has a better chance of not getting extinct.
Hence, the correct answer is C.
Note: Branching descent and Natural selection are the two concepts of the theory of evolution of Darwin. According to Darwinism all species of organisms arise and develop due to the natural selection of small inherited variations that increase the individual's ability to compete, survive, and reproduce.