Which fundamental particle is neutrino?

• A. Neutrino
• B. Quark
• C. Electron
• D. Photon

Answer: (A)

The key idea is recognizing the category of the particle in question and why neutrino fits as an elementary particle. A neutrino is one of the fundamental, or elementary, leptons in the Standard Model—it is not made of smaller components. It carries no electric charge and has an extremely small mass, and it interacts with matter mainly through the weak nuclear force (and gravity), which is why it’s so hard to detect.

This helps distinguish it from the other options. A quark is also considered fundamental, but it’s a building block that combines to form protons, neutrons, and other hadrons, not something a neutrino is. An electron is a different lepton with a negative electric charge, not what a neutrino is. A photon is a gauge boson that mediates electromagnetic interactions, not a fermion like a neutrino. So the neutrino is the fundamental particle in this context because it is an elementary lepton with those characteristic properties.