Two identical nuclei A and B of the same radioactive element undergo $\mathrm{\beta }$-decay. A emits a $\mathrm{\beta }$-particle and changes to A'.B emits a $\mathrm{\beta }$-particle and then a $\mathrm{\gamma }$-photon immediately afterwards, and changes to B'.

A' and B' are isotopes

A' and B' have the same atomic number and different mass numbers

A' and B' have the same atomic number and mass number

A' and B' have different atomic numbers but the same mass number