The decreasing values of bond angles from ${\mathrm{H}}_2\mathrm{O}$ $\left({104.5}^{\circ }\right)$ to ${\mathrm{H}}_2\mathrm{Te}\left({91}^{\circ }\right)$ down the group-16 of periodic table is due to:

As we move from ${\mathrm{H}}_2\mathrm{O}$ to ${\mathrm{H}}_2\mathrm{Te},$ the bond angle decreases. This is because as we move down in group 16, the bond length H-E increases, and consequently the repulsion between bond pairs decreases and the bond angle HEH decreases.

This is due to increasing p-orbital character in $s{p}^3$.

Hence, the option D is correct.