Atoms, nuclei and radiation — practice question

An atomic nucleus emits a $\beta$-particle. How do the proton number and nucleon number of the nucleus change as a result?

• Aproton number: $-1$; nucleon number: $+1$
• Bproton number: $0$; nucleon number: $-1$
• Cproton number: $+1$; nucleon number: $-1$
• Dproton number: $+1$; nucleon number: $0$