Answer: The correct answer is- C. over a long period of time.
Genetic diversity can be described as the sum of all the genetic characteristics, which correspond to the genetic makeup of all the organisms within a species.
Genetic diversity allows the organisms of a population to adapt to the changing environmental conditions as beneficial alleles allows the differential survival and reproduction of an organism.
Thus, a species develop genetic diversity over a long period of time that brings desirable modification or lead to the evolution of new species.