Carbon exists in nature as three isotopes. given the atomic masses and relative abundance of the isotopes, what is the average atomic mass of carbon?

Isotope is the same element but in another form.  They have the same number of protons but different number of neutrons in the nuclei. As a result they will have different atomic masses. In computing for the average atomic mass of carbon, their relative percent abundance and atomic masses of each of the isotopes will be needed. We then get the summation of the product of the atomic mass and percentage abundance. 

- decrease the number of plants and animals living in the water.

colorless gas, exhibiting a blue glow when placed in an electric field

b) solid

its a type of rock