Consider the following reaction: ${ }_{\mathrm{Z}}^{\mathrm{A}}\mathrm{X}{\to }_{\mathrm{Z}+1}^{\mathrm{A}}\mathrm{Y}{\to }_{\mathrm{Z}-1}^{\mathrm{A}-4}\mathrm{Z}{\to }_{\mathrm{Z}-1}^{\mathrm{A}-4}\mathrm{Z}$ Radioactive radiation emitted in the following sequence:

In $\beta$-emission, A remains same and Z increases by 1.
In $\alpha$-emission, A decreases by 4 and Z decreases by 2.
In ${\rm Y}$-emission, there is no change in A and Z.