b
Under ordinary conditions, NF \(_{3}\) does not hydrolyses via \(\mathrm{S}_{\mathrm{N}_{2}}\), mechanism because \(\mathrm{H}_{2} \mathrm{O}\) (which should act as a nucleophile) cannot attack any of Nitrogen or Fluorine atom due to absence of vacant orbitals of suitable energy.

But, under drastic conditions it gives \(\mathrm{N}_{2} \mathrm{O}_{3}\) and \(\mathrm{HF}\) via series of reactions involving 3 times \(\mathrm{S}_{\mathrm{N}_{1}}\) with deprotonation and then 2 times dehydration.