The correct order of bond angles (smallest first) in ${\text{H}}_2\text{S},{\text{NH}}_3,{\text{BF}}_3$ and ${\text{SiH}}_4$ is:

* ${\text{H}}_2\text{S}$ has $s{p}^3$ hybridization with two lone pairs, causing significant repulsion; its angle is $\approx 92^{\circ }$.${\text{NH}}_3$ has $s{p}^3$ hybridization with one lone pair; its angle is $107^{\circ }$.${\text{SiH}}_4$ has $s{p}^3$ hybridization with no lone pairs; it is a regular tetrahedron with $109.5^{\circ }$.${\text{BF}}_3$ has $s{p}^2$ hybridization; it is trigonal planar with $120^{\circ }$.
Order: ${\text{H}}_2\text{S}<{\text{NH}}_3<{\text{SiH}}_4<{\text{BF}}_3$.