They both have a plasma membrane and protoplasm.
They both contain DNA.
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.
Has an iron ion (and it's called haem btw)
A is correct one for that
