Answer:
Option B
Explanation:
Let us assume, a particle X having atomic number Z and mass number A.
when an $\alpha $- particle is emitted by a nucleus, then its atomic number decreases by 2 and mass number decreases by 4 . So , for given case,
$_{Z}X^{A}$ $\underrightarrow{4\alpha-particle}$ $_{Z-8}Y^{A-16}$
when a $\beta$- particle is emitted by a nucleus its atomic number increases by one and mass number remains unchanged. So, for given case,
$_{Z-8}Y^{A-16}$ $\underrightarrow{7-\beta particle}$ $_{Z-1}Y^{A-16}$
$\therefore$ Number of neutrons/ number of protons = $\frac{(A-16)-(Z-1)}{(Z-1)}$
= $\frac{A-Z-15}{(Z-1)}$
