Which of the following best explains what is happening when an atom emits light

A) An electron is dropping from a higher to a lower energy level with the difference in energy between the two being emitted as light energy.
B) A proton is undergoing a nuclear change in the nucleus and is emitting a high energy light wave in the process.
C) An electron is jumping from a low energy state to a high energy state with the difference in energy being converted to light energy.
D) Heat energy is speeding up the orbit of the electrons and the resulting Doppler shift causes light to be emitted from the electrons.
E) Heat energy is converting a neutron into a proton and an electron, which is ejected into the orbit of the nucleus, releasing light energy.