Which among the following gases liquefy easily?

The temperature and pressure at which ice,liquid water,and water vapour can exist together are:

The number of statements,which are correct with respect to the compression of carbon dioxide from point $(a)$ in the Andrews isotherm from the following is $..........$.
$A.$ Carbon dioxide remains as a gas up to point $(b)$
$B.$ Liquid carbon dioxide appears at point $(c)$
$C.$ Liquid and gaseous carbon dioxide coexist between points $(b)$ and $(c)$
$D.$ As the volume decreases from $(b)$ to $(c)$,the amount of liquid decreases

The critical temperatures $(T_C)$ of some gases are given below:

Gases	$H_2, He, O_2$
$T_C \ (K)$	$33.2, 5.3, 154.3$

Based on the above data,what is the order of liquefaction of these gases? Start writing the order from the gas that liquefies first.

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

Which of the following conditions is most favorable for the liquefaction of a gas?