Some of these can easily be eliminated by knowing that both nitrogen 14 and nitrogen 15 are isotopes ( same element, with the same amount of protons, but with different numbers of neutrons) of nitrogen. So if the only difference between nitrogen 14, 15 , and regular nitrogen is the amount of neutrons...how many protons and electrons should both nitrogen 14 and 15 have? After thinking, you should be able to eliminate A, B,and C.
Out of the following choices, fossil fuels is the largest reservoir of carbon in the world. A couple of other reservoirs of carbon are dissolved in the ocean and in plants.
