Minimum de-Broglie wavelength is associated with

$\begin{array}{l}\mathrm{\lambda }=\frac{\mathrm{h}}{\mathrm{mv}}.\mathrm{For}\mathrm{same}\mathrm{velocity}\mathrm{\lambda }\propto \frac{1}{\mathrm{m}}.\\ {\mathrm{SO}}_2\mathrm{molecule}\mathrm{has}\mathrm{least}\mathrm{wavelength}\mathrm{because}\text{\hspace{0.17em}\hspace{0.17em}its\hspace{0.17em}\hspace{0.17em}}\mathrm{molecular}\mathrm{mass}\mathrm{is}\mathrm{high}.\end{array}$