Van der Waal's equation $\left[ p + \frac{a}{V^2} \right] (V - b) = nRT$ is applicable for

In the following compressibility factor $(Z)$ versus pressure graph at $300 \, K$,the compressibility of $CH_{4}$ at pressure $< 200 \, bar$ deviates from ideal behaviour because

The compressibility factor $(Z)$ of a gas is less than unity at $STP$,then:

Real gases deviate from ideal behaviour because the molecules

The correction factor '$a$' in the van der Waals equation for real gases corresponds to:

Why do real gases deviate from ideal behavior in the $pV$ vs $p$ and $p$ vs $V$ graphs at specific temperatures?