Scientists produced the first artificial radioactive substance by firing $\alpha$-particles at aluminium, $^{27}_{13}\text{Al}$. The result was an unstable isotope of phosphorus, $^{30}_{15}\text{P}$. What was produced as the by-product of this reaction?
- Aan $\alpha$-particle
- Ba $\beta$-particle
- Ca neutron
- Da proton