Answer: A. an electron
<u>Beta particles are electrons or positrons (electrons with positive electric charge or antielectrons).</u> Beta decay is a type of radioactive decay in which a beta ray is emitted from an atomic nucleus.
<u>Beta decay occurs when, in an unstable nucleus with too many protons or too many neutrons, one of the protons or neutrons transforms into the other.</u> In beta minus decay, a neutron is broken down into a proton, an electron, and an antineutrino (the neutrino antiparticle, meaning it has an opposite charge to the neutrino). In beta decay plus, a prototype breaks down into a neutron, a positron and a neutrino.
