On bombardment of ‌11H proton, an α -particle will comes out as follows: ‌8O16+‌1H1→‌7N13+‌2He4 Sum of mass number Reactant side =16+1=17 Product side =13+4=17 Sum of atomic number Reactant side =8+1=9 Product side =7+2=9 As bombarding particle, ‌1H1 is can be written as proton (p) and ejecting particle can be written as (α). The whole reaction can be summarised as follows: ‌8O16(p,α),N13 Hence, (a) is the correct option.