Answer: C. mutation in an organism's DNA
Step-by-step explanation:
A lack of predators will not pressure a population to adapt or evolve, so no large changes would take place. This is also true for an abundance of natural resources. Underproduction of offspring is something that may affect a population, but this isn't something that will change genotypes or phenotypes of populations in order to adapt to this. Mutations in the DNA of organisms don't always result in a different trait, but when it does, natural selection will act on it; if it's favorable, it will become more prevalent as the new trait passes down onto offspring