The answer is D. The natural selection is a theory which illustrates the gradual process of evolution in the population due to the change of environment. The key point is the mutation (variation) exists in the population before the environment changing. For C, if the environment does not change, though the adaptation is useful to environment, it will not be selected. Because the organisms without the adaptation will not die.
That one difference is that a women’s voice box has a much higher vibration and a Male’s voice box has a much lower and deeper vibration when they get older.
Hope this helps :)
You're either talking about Community which means grouping of different organs or population which is the grouping of the same organ