The seeds she planted in the mud grew quicker because the mud is holding nutrition for the corn. The soil is a good guess to make, but the mud is more dense and moist. The water wouldn't have had more nutrients than the mud, just because the mud holds breakdown matter and other things from other plants.
Change in the external Environment may resulted in the changing in the population of beetles.
Please rephrase the question, it doesn't make sense.
I believe another term for Natural Selection, based off of the answers provided, I would say C, Survival of the Fittest.
