Which of the following transition leads to the emission of high energy photons?

D

During emission, the electron make a transition from higher excited state to lower excited state. The energy of n^th excited state is given by 

E_n = -13.6/n²

So, E₂-E₁ = 10.2 eV

E₃-E₁ = 12.09 eV

This clearly shows that the transition D will release high energy photon.