In the $Vander$ $Waals$ equation,the constant $'b'$ is a measure of $......$.

The deviation will be maximum in the behaviour of a gas from the ideal gas equation $PV = nRT$?

What is the compressibility factor of a gas at high pressure?

The correct equation for one mole of a real gas is ($a, b$ are constants)

Under which one of the following conditions do real gases approach the ideal gas behaviour?

For real gases,the van der Waals equation is written as $\left( p + \frac{a n^2}{V^2} \right) (V - nb) = nRT$,where $a$ and $b$ are van der Waals constants. Two sets of gases are:
$(I)$ $O_2, CO_2, H_2, He$
$(II)$ $CH_4, O_2, H_2$
The gases given in set-$I$ are arranged in increasing order of $b$,and the gases given in set-$II$ are arranged in decreasing order of $a$. Select the correct order from the following: