The correct answer is Liquid Ammonia.Ammonia is used in the refrigerator to cool the water.Refrigerator consists of devices that compress and expand refrigerant gas.When gas is compressed, it expels heat and when it is expanded, it absorbs heat, thereby, producing cooling.Additional InformationLiquid Hydrogen is a fuel used in Rocket Engines.Liquid nitrogen uses mainly based on its cold temperature and low reactivity.Liquid Helium is used in numerous applications in cryogenics, magnetic resonance imaging (MRI), and superconducting magnets.