Which energy transition may take place in the atom if its electron has absorbed a photon? a-n = 5 to n = 1 b-n = 3 to n = 2 c-n = 5 to n = 2 d-n = 1 to n = 3 e-n = 3 to n = 1

Answer is "D".

When an electron absorbs a photon, the energy of the electron will be high. Then that electron cannot remain on the same energy level. Hence, that electron will go to a higher energy level from the ground state. Hence, the energy transition should be from lower energy level to higher energy level.