dit-pr bonding is shown in
(a) $\mathrm{P}_{2} \mathrm{O}_{3}, \mathrm{P}_{2} \mathrm{O}_{5}, \mathrm{PO}_{4}{ }^{3}-$
(b) $\mathrm{CO}, \mathrm{NO}, \mathrm{CO}_{2}, \mathrm{NO}_{2}$
(c) $\mathrm{NH}_{3}, \mathrm{PH}_{3}, \mathrm{BiH}_{3}$
(d) $\mathrm{NO}_{3}^{-}, \mathrm{NO}_{2}-\mathrm{N}^{3-}, \mathrm{CN}^{-}$