Gate 2008 : nuclear physics

I think answer a

but in this question, I faced a one problem that I intial momentum of meson is not coming equal to the momentum of photons

see this solution... the total energy of meson that is the initial energy is 175Mev. so when u add the energy of options 3and 4 u get 175MeV. so option c,d is correct...

0.83*10^(-16)

what is the lifetime of pion