Given the masses of various atomic particles  mp=1.0072 u,  mn=1.0087u,  me=0.000548 u, mv¯=0, md=2.0141u, where P = portion, n = neutron, e = electron,  v¯  = antineutrino and d = deuteron.  Which of the following process is allowed by momentum and energy conservation?

n+n→ deuterium atom is not energetically feasible as mass on product side is more than mass on reactant side.p→n+e++ν−  is also not energetically feasible.e++e−→γ  is not possible as momentum conservation does not hold.rather e++e−→2γ would be correct.As n+p→d+γ is energetically feasible  as mass on product side is less than mass on reactant side, it could be possible.