Which listed gas has been used improperly for artificial fruit ripening and is prohibited for that purpose by FSSAI?

Explanation

Acetylene, sometimes called carbide gas in this context, has been used improperly for artificial fruit ripening. FSSAI prohibits its use for that purpose. Ethylene is the gas associated with regulated ripening practices, but it is not among these options. The question identifies the prohibited gas rather than recommending its use.