The statement that is true about stable isotopes is: A stable nucleus has a similar number of protons and neutrons.
In general, for lighter elements, stable isotopes tend to have roughly equal numbers of protons and neutrons. As the atomic number increases, the ratio of neutrons to protons in stable isotopes can increase to maintain stability, but a significant disparity in numbers often leads to instability. The other statements are incorrect as they misrepresent the nature of isotopes and stability.