Atoms, nuclei and radiation — practice question

When a nucleus emits an $\alpha$-particle, what changes occur in the proton number and the nucleon number of the nucleus before the emission?

• Aproton number $-4$, nucleon number $-2$
• Bproton number $-2$, nucleon number $-2$
• Cproton number $-2$, nucleon number $-4$
• Dproton number $+1$, nucleon number no change