(i) $NO_{2}^- \Rightarrow 2 \sigma+1 I p=3, i .e$ $sp ^{2}$ hybridisation

(ii) $N H_{3} \Rightarrow 3 \sigma+1 I p=4, i .e$ $sp ^{3}$ hybridisation

(iii) $B F_{3} \Rightarrow 3 \sigma+0 I p=3, i .e$ $sp^2$ hybridisation

(iv) $N H_{2} \Rightarrow 2 \sigma+2 I p=4, i.e$ $sp ^{3}$ hybridisation

(i) $H_{2} O \Rightarrow 2 \sigma+2 I p=4, i.e$ $sp ^{3}$ hybridisation

Thus, among the given pairs, only $B F_{3}$ and $N O_{2}^-$, have $s p^{2}$ hybridisation.