Answer:
C.
Explanation:
All these carbon atoms are isotopes: they have the same amount of protons (in this case, 6 because carbon always has 6 protons) and the same amount of electrons (6 because the carbons given have a neutral charge).
Therefore, the only thing we are changing is the atomic mass and the amount of neutrons present in each isotope.
In Carbon-12, there are 6 protons, 6 neutrons, and 6 electrons.
In Carbon-13, there are 6 protons, 7 neutrons, and 6 electrons.
In Carbon-14, there are 6 protons, 8 neutrons, and 6 electrons.