The correct option is D Genetic drift
Answer is option C i.e. "Genetic drift"
Five basic assumptions of Hardy-Weinberg law are: random mating, infinite (large) population size, no mutation, no gene flow and no selection.
While, genetic drift occurs in small size population. Genetic drift is a type of evolution that is not necessarily adaptive. It does not specifically selection for traits that are fit for the environment. Hence, answer is "Genetic drift"