Which of the following nuclear reactions will generate an isotope?

Isotopes are atoms of the same element (same atomic number $Z$) with different mass numbers ($A$).Neutron emission: ${}_Z^{A}X\to {}_Z^{A-1}X+{}_0^{1}n$. Here, $Z$ remains same, $A$ changes. This produces an isotope.Positron emission: $Z$ decreases by 1.$\alpha \text{-emission}$: $Z$ decreases by 2, $A$ decreases by 4.$\beta \text{-emission}$: $Z$ increases by 1.