b
For \(s p^{2}\) hybridisation, there must be \(3 \sigma\) -bonds or 2 c-bonds along with a lone pair of electrons.

(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.