d
\((A) \,O _3\) molecule undergoes \(sp^2\) hybridisation, so its bond angle is nearly \(120^{\circ}\)

\((B) \,I_3^-\) undergoes \(sp^3 d\) hybridisation and linear shape so its bond angle is \(180^{\circ}\).

\((C) \,NO _2^{-}\) undergoes \(s p^2\) hybridisation and So, its bond angle is nearly \(120^{\circ}\)

\((D) \,PH _3\) undergoes \(sp ^3\) hybridisation and contains one lone pair, so its bond angle is mearly \(90^{\circ}\)

\(\therefore\) Among all the options, \(PH _3\) has least angle around the central atom.