Explanation

(d) A beta minus particle ($\beta^{-}$) is an electron. Emission of $\beta^{-}$ involves transformation of a neutron into a proton, an electron and a third particle called antineutrino ($\overline{v}$).
${\ \ \ \ \ \ \ \ \ }_{0}n^{1}\ = \ \ _{1}p^{1}\ + \ \ _{- 1}\beta^{0} + \overline{v}$