Which of the following are considered the fundamental building blocks of atoms?

The choice stating protons, neutrons, and electrons as the fundamental building blocks of atoms is correct because these particles make up the majority of atomic structure. Protons and neutrons reside within the nucleus of an atom, while electrons orbit around this nucleus. Protons carry a positive charge, neutrons are neutral, and electrons carry a negative charge, which allows them to interact with each other through electromagnetic forces, holding atoms together.

In contrast, the other options include entities that either do not form the basic structure of an atom or involve subatomic particles in a broader context. Photons, electrons, and muons are not all components of an atom, as photons are particles of light and do not contribute to mass or structure. Atoms, molecules, and ions represent larger constructs made from the fundamental particles, not the fundamental particles themselves. Lastly, while nuclei, quarks, and leptons are components of matter, in the context of atomic structure, protons and neutrons (which are themselves composed of quarks) and electrons are more immediate representatives of what constitutes an atom.