What do all pairs of leptons consist of?

In the context of the Standard Model of particle physics, all pairs of leptons consist of an electrically charged particle and a neutrino. Leptons are fundamental particles that do not undergo strong interactions. The most familiar charged lepton is the electron, which has a negative charge, while the associated neutrino is the electron neutrino, which is neutral and very light, making it difficult to detect.

Each type of charged lepton (such as the muon or tau) is also paired with a corresponding neutrino (muon neutrino and tau neutrino, respectively). Thus, each lepton family consists of one charged lepton and one neutrino. This pairing exemplifies the structure and characteristics of leptons within the particle framework.

Other choices do not represent the correct structure of leptons. For instance, pairs of neutrinos do not consist of charged leptons at all; charged particles cannot be paired without their corresponding neutral partners. Additionally, a proton is not a lepton; it belongs to the category of baryons, which are subject to strong interactions and are thus distinct from leptons.