A nucleus undergoes an α decay followed immediately by a β− decay. What is the net change in its atomic number Z and mass number A after the two decays?
(a) Z decreases by 3 and A decreases by 4
(b) Z decreases by 2 and A decreases by 4
(c) Z decreases by 1 and A decreases by 4
(d) Z is unchanged and A decreases by 4