Question

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

Explanation:

Protons and neutrons are made of quarks. Nucleus contains protons and neutrons. Electrons are not made of quarks. So the particle labeled X enclosing quarks is likely a proton or neutron.

Answer:

It is either a proton or a neutron.