Mean Free Path & Real Gases question from JEE Main 2020 (8 Jan, Shift 1)

Answer: (b)

1. Mean free time $t = \dfrac{\lambda}{\bar v}$, with $\lambda = \dfrac{1}{\sqrt{2}\,n\pi d^2}$ fixed for a fixed number density.
2. $\bar v \propto \sqrt{T}$, so $t \propto \dfrac{1}{\sqrt{T}}$.
3. A plot of $t$ against $\dfrac{1}{\sqrt{T}}$ is a straight line with positive slope.
4. So the answer is (b).