For which of the following is the van der Waals equation valid?

If $Z$ is a compressibility factor,the van der Waals equation at low pressure can be written as:

Explain: Why do real gases show deviation from ideal gas behavior?

The variation of the compressibility factor $(Z)$ with pressure $(P$ in $bar)$ for some gases is shown in the figure below. Identify the gases $(A)$, $(B)$, and $(C)$.

The $Z$ vs $P$ graph for four gases is given below at the same temperature.
Which of the gases will have the highest value of critical temperature $(T_c)$?

Which of the following indicates a plot of compressibility factor $(Z)$ $vs$ $p$ at room temperature for helium?