Hybridisation is determined from the steric number (number of atoms bonded to the central atom + the number of lone pairs). Number of hybrid orbitals must be equal to the steric number.

From the Lewis structure.

(i) Steric number of N-atom $=3$ (2 bonded atoms +1 lone pair), $\therefore$ Hybridisation $=s{p}^2$ (3 hybrid orbitals).

(ii) Steric number of C-atom $=2$ (2 bonded atoms),

$\therefore$: Hybridisation $=s p$ ( 2 hybrid orbitals).

(iii) Steric number of 0 -atom $=3$ (1 bonded atom +2 lone pair) $\therefore$ Hybridisation $={\mathrm{sp}}^2(3$ hybrid orbitals).