When an electron of an atom returns from an excited state to the ground state, it emits energy in the form of a photon. how does the change in energy level compare to the energy of the emitted photon?

a. it is less than the energy of the photon.
b. it is about one third the energy of the photon.
c. it is exactly half of the energy of the photon.
d. it is equal to the energy of the photon.
e. it is exactly twice the energy of the photon.