Radioactive Decays: Alpha, Beta, Gamma question from MHT CET 2023 (13 May, Shift 1)

Answer: (b)

1. An isotope needs the same $Z$ as the original nucleus.
2. One $\alpha$ lowers $Z$ by 2; each $\beta^-$ raises $Z$ by 1.
3. Net $\Delta Z = -2 + 2 = 0$ needs exactly two $\beta$ with one $\alpha$.
4. So the answer is (b) one $\alpha$ and two $\beta$.