The understanding of evolutionary processes has scientists in the field of artificial selection. the best example of artificial selection is

The conservation of bald eagles is not a description of selective breeding, but it could be. For now we can cross that off.
Geographical distribution is a geographical factor of Natural selection, so it can't be B either.
Pesticide-resistant potatoes are altered to be resistant to pesticides (pesticides wouldn't affect plants anyway as they are meant to kill insects)
The answer is D. The collection and reseeding of the largest pumpkins is the best answer.