A radioactive nucleus $^A_ZX$ undergoes spontaneous decay in the sequence $^A_ZX\rightarrow{}_{Z-1}B\rightarrow{}_{Z-3}C\rightarrow{}_{Z-2}D$, where $Z$ is the atomic number of element X. The possible decay particles in the sequence are:
A $\alpha,\ \beta^+,\ \beta^-$
B $\beta^+,\ \alpha,\ \beta^-$
C $\beta^-,\ \alpha,\ \beta^+$
D $\alpha,\ \beta^-,\ \beta^+$