What are the subatomic particles that make up an atom?

The correct answer encompasses the three main subatomic particles that constitute an atom: protons, neutrons, and electrons. Protons are positively charged particles found in the nucleus of an atom and are responsible for defining the element's identity (as different elements have different numbers of protons). Neutrons are neutral particles that also reside in the nucleus and contribute to the atom’s mass, helping to stabilize the nucleus by offsetting the repulsive forces between protons. Electrons are negatively charged particles that orbit the nucleus in various energy levels or shells, playing a crucial role in chemical bonding and the atom's overall charge.

This combination of protons, neutrons, and electrons is fundamental to the structure and behavior of matter, making option B the accurate representation of an atom's composition. Other choices include particles that either do not exist in the context of atoms, like muons and positrons, or substitute neutrinos, which are elementary particles that interact very weakly with matter and are not part of atomic structure.