Nerve, Skin, Cyclins, Cancer
The condensation of water vapor formed the early oceans. It is an important part of the water cycle. It is easy to eliminate the other answers in this question. It can't be meteorites, living organisms, or nitrogen.
Human activities in the united states such as burning fossil fuels for electricity, heat, and certain transportation.
hope this helps :)
Plants leafs increasing carbon dioxide. it's remove dust air pollution
Yes it could change the park if you remove a population from the national park
