Answer
Quantum Chromodynamics explains the confinement of quarks in mesons and baryons. Quarks are the fundamental particles that make up protons and neutrons. They are held together by the strong force, which is mediated by gluons. The strong force is so strong that it prevents quarks from being separated from each other. This is why quarks are never found in isolation, but only as part of mesons and baryons.