Answer:
(c) Low temperature, high pressure
Explanation:
Liquefaction of a gas means the conversion of the gas to liquid. To convert a gas to liquid, we have to look a bit at the statements of the kinetic theory of gases.
Gases show ideal behavior within the range of high temperature and low pressure. Under these conditions, minimum intermolecular interactions occur between gas molecules.
However, as the temperature is deceased and pressure in increased, intermolecular interactions become significant and the gas begins to liquefy.