The diagram below shows some subatomic particles.

which of these statements best identifies the particle that is labeled with an x?
it is either an electron or an isotope.
it is either a proton or a neutron.
it is either a beta particle or a nucleus.
it is either a neutron or an electron.

The correct option is this: IT IS EITHER A PROTON OR A NEUTRON.

Each atom of an element is made up of three sub particles, these are: electrons, protons and neutrons. The protons and the neutrons are located inside the nucleus of the atom while the electrons are located outside the nucleus, where they orbit round the nucleus. Since the sub particle X given in the question is located in the nucleus of the atom, then it is either a proton or a neutron.