Real gases deviate from ideal behaviour because the molecules

Identify the conditions at which the van der Waals equation of state changes to the ideal gas equation.

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:

Under which conditions does the $van \ der \ Waals$ equation reduce to the ideal gas equation?

At high pressure,the van der Waals equation for a real gas reduces to: