The correct option is D It cannot be liquefied at any value of P and T
A gas can be liquified only if there is intermolecular attractive forces occuring among the gas particles. A gas with non-zero intermoleular force (i.e., any real gas) can be liquified by applying the pressure provided the temperature is less than its critical temperature (TC). In ideal gas, there is no intermolecular attraction and hence the gas cannot be liquified at any value of P and T.