Which elementary particles combine to form protons and neutrons?

Protons and neutrons, which are collectively known as nucleons, are composed of fundamental particles called quarks. Quarks come in different types or "flavors," which are up, down, charm, strange, top, and bottom. A proton is made up of three quarks: two up quarks and one down quark, while a neutron consists of one up quark and two down quarks. The interactions between quarks are governed by the strong force, which is mediated by particles known as gluons. This combination of quarks is essential for the formation of protons and neutrons, making quarks the correct choice in the context of this question.

Other particles like electrons, neutrinos, and photons do not combine to form protons and neutrons. Instead, electrons are elementary particles that are part of atoms but do not contribute to the mass of nucleons. Neutrinos are very light particles that interact very weakly with matter and do not contribute to the structure of protons and neutrons either. Photons are particles of light and are responsible for electromagnetic interactions but are not involved in the composition of protons or neutrons. This context helps clarify why quarks are the elemental building blocks in question.