Which of the following effect is responsible for the production of light in an electric discharge lamp?

Correct option is C

​$$\text{In an electric discharge lamp, light is produced due to the ionization of gas or vapour inside the lamp:} \\[8pt]\bullet \ \text{When a high voltage is applied across the electrodes, it ionizes the gas/vapour (such as neon, mercury vapour, sodium vapour).} \\[4pt]\bullet \ \text{The ionized atoms get excited and, on returning to a lower energy state, emit light.} \\[4pt]\bullet \ \text{This emitted radiation may be directly visible (as in neon lamps) or ultraviolet, which is then converted to visible light using a phosphor coating (as in fluorescent lamps).}$$​​