Wich subatomic particles will you add or remove to change the mass of an atom? A) electrons and protons B) protons or neutrons C) electrons or neutrons D) Electrons only

Technically all subatomic particles have a mass, however, electrons have such a small mass, they are insignificant and generally ignored. On the other hand, the mass of a proton and neutron are substantial, so B would be the correct answer.