The correct option is B Neutron
In the following nuclear reaction, 2713Al+42He→3015P+10X, X is neutron. Neutron has zero charge and mass of 1 amu approximately.
On Left hand side, sum of atomic numbers =13+3=15.
On right hand side, sum of atomic numbers =15+0=15 .
Hence, the sum of the atomic numbers is same on both sides.
On Left hand side, sum of mass numbers =27+4=31.
On right hand side, sum of mass numbers =30+1=31.
Hence, the sum of the mass numbers is same on both sides.