For a nucleus undergoing beta decay, its atomic number increases by 1. This implies the decay emits which of the following particles?
Correct: A
In beta-minus decay, a neutron converts into a proton, emitting an electron ($ \beta^- $) and an antineutrino. This increases the atomic number by 1, making option A correct. Students must recall beta decay mechanisms and the transformation of quarks within neutrons.