Which of the following particles has zero-charge?

1. A

   Positron

   (a) Positron. The positron is the electron’s antiparticle with charge +1e, not zero.

2. B

   Neutrino

   (b) Neutrino. Neutrinos are electrically neutral leptons; they interact only via the weak force (and gravity). Zero charge is the official key.

3. C

   Electron

   (c) Electron. The electron carries charge −1e.

4. D

   a-particle

   (d) α-particle. An alpha particle is a helium-4 nucleus, charge +2e.

Summary. Official key is (b) Neutrino. Among the four, only the neutrino has zero electric charge. The positron is positive, the electron negative, the alpha particle doubly positive. A neutron is also neutral but is not on this list; do not confuse neutron with neutrino. Neutrinos come in electron, muon and tau flavours.