The table shows a comparison of the penetrating power and ionising effect of $\alpha$-radiation and $\gamma$-radiation. Which row is correct?
- Aleast penetrating: $\alpha$; most ionising: $\alpha$
- Bleast penetrating: $\alpha$; most ionising: $\gamma$
- Cleast penetrating: $\gamma$; most ionising: $\alpha$
- Dleast penetrating: $\gamma$; most ionising: $\gamma$