If the rest mass of electron or positron is 0.51 MeV, then the kinetic energy of each particle in the electron-positron pair production by a -photon of 2.42 MeV will be 

• A

  0.3 MeV 

• B

  1.9 MeV   

• C

  0.7 MeV 

• D

  1.5 MeV