At which of the following conditions can a gas be liquefied? ($T_c$ and $P_c$ are critical temperature and pressure.)

Under what conditions will an ideal gas,which follows the kinetic gas equation,undergo liquefaction?

However great the pressure,a gas cannot be liquefied above its

Isotherms of carbon dioxide gas are shown in the figure. Mark a path for changing gas into liquid such that only one phase (i.e.,either a gas or a liquid) exists at any time during the change. Explain how the temperature,volume,and pressure should be changed to carry out this process.

What are the most favourable conditions to liquefy a gas?

Which statement$(s)$ is/are applicable above critical temperature?