Which of the following is redox reaction

(A) ${\mathrm{H}}_2{\mathrm{SO}}_4+2\mathrm{NaOH}\to {\mathrm{Na}}_2{\mathrm{SO}}_4+2{\mathrm{H}}_2\mathrm{O}$;  no change in oxidation states, not a redox reaction.

(B) ${\stackrel{0}{\mathrm{O}}}_2\to {\stackrel{0}{\mathrm{O}}}_3$  ;  no change in oxidation states, not a redox reaction.

(C) ${\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to {\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$ ; no change in oxidation states, not a redox reaction.

(D) $\stackrel{+4}{\mathrm{N}} \stackrel{-2}{{\mathrm{O}}_2} \to \stackrel{0}{ {\mathrm{N}}_2}+\stackrel{0}{{\mathrm{O}}_2}$ ; N reduces and O oxidizes, So it is a redox reaction.