Final answer:
The true statement about an antineutrino emitted in beta decay is option b. that it has no electric charge. Antineutrinos are neutrally charged particles with negligible mass, produced during beta-minus and beta-plus decay processes, which also involve electrons and positrons, respectively.
Step-by-step explanation:
Among the options provided, the correct statement about an antineutrino emitted in beta decay is that it has no electric charge. Antineutrinos are produced in beta decay processes along with electrons (in beta-minus decay) or positrons (in beta-plus decay). These particles are part of the lepton family and are known for their very small or negligible rest mass and lack of electric charge. The mass of an antineutrino is not equivalent to the mass of a neutron or a proton, and it does not have a negative charge either.
In beta-minus decay, a neutron is converted into a proton and an electron (beta particle), with the emission of an antineutrino. In beta-plus decay, a proton is transformed into a neutron, and a positron (antielectron or beta-plus particle) is emitted along with an antineutrino. The conservation of both electric charge and lepton family number is maintained in these processes.