Species have similar characteristics, but they are rarely, if not never, identical; the difference between them is variation!
Hope this helps! :)
It is an essential element for plant life, but when there is too much of it in water, it can speed up eutrophication (a reduction in dissolved oxygen in water bodies caused by an increase of mineral and organic nutrients) of rivers and lakes. Soil erosion is a major contributor of phosphorus to streams.
There is no answer that is right except for C. Natural Selection.
Genetic Recombination doesn't change gene frequency;nor does migration. (Unless it's local)
Mutation could be the answer, but since mutations are too rare to really power Evolution, the only logical answer is Natural Selection.
