Among H_ 2 ~S, H_ 2 O, NF_ 3 , NH_ 3 and CHCl_ 3 , identify the...

Comparing dipole moments:
$H_2S$ ≈ 0.97 D (bent, 2 lone pairs on S),
$H_2O$ ≈ 1.85 D (bent, 2 lone pairs on O),
$NF_3$ ≈ 0.24 D (pyramidal, 1 lone pair on N),
$NH_3$ ≈ 1.42 D (pyramidal, 1 lone pair on N),
$CHCl_3$ ≈ 1.04 D (tetrahedral, 0 lone pairs on C).
$NF_3$ has the lowest dipole moment because the highly polar N-F bonds are oriented in such a way that their contributions nearly cancel with the effect of the lone pair. The central atom in $NF_3$ is N, which has 1 lone pair of electrons.