The correct answer is D. mesons.
Mesons are subatomic particles that are made up of a quark and an antiquark. They are unstable and decay into other particles very quickly. Mesons are found in the nucleus of atoms, where they help to hold the nucleons (protons and neutrons) together.
Electrons are subatomic particles that have a negative charge. They are found outside the nucleus of atoms, where they orbit the nucleus. Electrons are responsible for the chemical properties of atoms.
Positrons are subatomic particles that have a positive charge. They are the antiparticles of electrons. Positrons are very unstable and decay into other particles very quickly.
Neutrons are subatomic particles that have no charge. They are found in the nucleus of atoms, along with protons. Neutrons help to hold the nucleus together.
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