Answer:
Potassium (k)
Explanation:
Potassium is so reactiev that it wont even be found naturally in nature, it legit racts with almost anything and doesn't take almost anything at all to start a reaction. COmpared to the other Potassium is easily number 1
Combustion is the burning of a substance. It could be complete or could be incomplete. It changes the form of carbon and so it plays it's role in cycle
I think its C.
I hope this helps and please do correct me if im wrong.
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.
Harmful because they change how the genes are supposed to form and they can give disorders at times.
