Give reasons for the following:(i) $\mathrm{(CH_3)_3P}=0$ exists but $\mathrm{(CH_3)_3N=O}$ does not.(ii) Oxygen has less electron gain enthalpy with negative sign than sulphur.(iii) $\mathrm{H_3PO_2}$ is a stronger reducing agent than $\mathrm{H_3PO_3}$.