The products in a decomposition reaction include an element and a compound are compounds are elements can be elements or compounds

I believe the answer is  can be elements or compounds
In this case, elements in the decomposition reaction is the substance that cannot be separated into simpler substances.
Compounds, technically act as a reactant in the decomposition reaction, but since the reaction breakdown one substance into two or more, sometimes it exists in the product.

Acid precipitation should be a concern for the new age environmentalist, as they are one of the many consequences of a polluted and warming world, such is the one we live in. Acid precipitation comes from the evaporation of acid sea water, due to global warming and the fact that when more heat is trapped into the sea, more acid substance are released.

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It can be answered by science because it is a question that is been solved via some experiments and it is in fact been proven recently as proofs correlates global waming with the acidification of the ocean and then acid rain. So this is a physic and environmental question, with ramification and consequences in other fields of science.

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Acid precipitation in forests could affect the reproduction rate in birds. There are multiple factor that affect the reproduction rate in birds, and environment is one of the most complex and yet undiscovered. The two could have a potential entaglement as, for hyphotesis, acid precipitation could cause certain plant to die, and than the birds do not have a place where to reproduce.

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It can be answered by science, via experiments and study. The relationship between environment and biology is a well-know correlation, so it does not represent a strech in this sense. Moreover, while it could be difficult to assure this for different reason, this is a problem that science could solve in different ways.