Which notations represent atoms that have the same number of protons but a different number of neutrons?

Atoms of the same element, containing the same number of protons, but different numbers of neutrons, are known as isotopes. Isotopes of any given element all contain the same number of protons, so they have the same atomic number (for example, the atomic number of helium is always 2).

Bthats what im doing to and i figured it out it is b