A radioactive nucleus ZAX Z-1B Z-3C Z-2D, where Z is the atomic number of element X. The possible decay particles in the sequence are :
(4) +, , -
-decay: Z decreases by 2; --decay: Z increases by 1; +-decay: Z decreases by 1.
X (Z) B (Z-1): Z falls by 1 +
B (Z-1) C (Z-3): Z falls by 2
C (Z-3) D (Z-2): Z rises by 1 -
Sequence: +, , -
Answer: (4)
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