= 6.63X1034 Js)(3.00X108 m/s)/568X10-9m = 3.50X10-19 J
This photon energy is equal to the energy difference between levels 2 and 3, i.e. (6.3 - 2.8) X 10-19J. and no other pair of levels.
Moreover the transition of the electron from the 2nd to the 3rd level is permitted by the Pauli Principle. Assuming that absorption does occur the answer is D