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

$A$ gas can be liquefied at temperature $T$ and pressure $p$ provided:

Which of the following statements is correct regarding the critical temperature $(T_c)$?

The statement that is $NOT$ correct is

What happens when $CO_2$ is compressed and expanded at a constant temperature of $30.98 \, ^\circ C$?

$A, B, C$ and $D$ are four different gases with critical temperatures $304.1, 154.3, 405.5$ and $126.0 \ K$ respectively. While cooling the gas,which gets liquefied first?