The Mean Free Path $\mathcal{l}$ for a gas molecule depends upon diameter, d of the molecule as

• A

  $\mathrm{\ell }\propto \frac{1}{\mathrm{d}}$

• B

  $\mathrm{\ell }\propto \frac{1}{{\mathrm{d}}^2}$

• C

  $\mathrm{\ell }\propto \mathrm{d}$

• D

  $\mathrm{\ell }\propto {\mathrm{d}}^2$