Bond angle is minimum for

$\begin{array}{llll} {\mathrm{H}}_2\mathrm{O}& {\mathrm{H}}_2\mathrm{S}& {\mathrm{H}}_2\mathrm{Se}& {\mathrm{H}}_2\mathrm{Te}\\ 104{.5}^{\mathrm{o}}& 92{.1}^{\mathrm{o}} & {91}^{\mathrm{o}}& {90}^{\mathrm{o}}\end{array}$

As we go down the group electronegativity decreases due to which repulsion between bonded pairs of electron also decreases. Hence, bond angle decreases.