A Beta decay is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted from an atomic nucleus. During a negative beta decay $\beta^{-}$, which of the following happens?

Question

$(a)\;an\;atomic\;electron\;is\;ejected\qquad(b)\;an\;electron\;which\;is\;already\;present\;within\;nucleus\;inejected\qquad(c)\;a\; neutron\;in\;nucleus\;decays\;emitting\;an\;electron \qquad(d)\;None$