Answer:
the valid answer is C mass numbers
Step-by-step explanation:
The isotopes have the same atomic number of the element. It means they have the same amount of protons and electrons, when we talk about a neutral atom. BUT they have a different number of neutrons. The neutrons are atomic subparticles that belongs to the nucleus and modify the atomic mass of the element.
All elements have isotopes due to in nature there is different natural occurrence abundance for each one.