Answer:
Option B
Explanation:
Y(n, $\alpha$) the nucleus splits in to $\alpha$- particle and neutrons
i.e, $_{Z}Y^{A}+_{0}n^{1}\rightarrow_{3}Li^{7}+_{2}He^{4}$
and Z+0=3 +2 or Z=5
So, A+1=7+4
A=10
Hence , the nucleus of element Y is boron
$_{5}Y^{10}=_{5}B^{10}$