The redox reaction among the following is:

Combination of dinitrogen with dioxygen at $2000 \mathrm{~K}$

Formation of ozone from atmosphereic oxygen in the presence of sunlight

Reaction of $\mathrm{H}_{2} \mathrm{SO}_{4}$ with $\mathrm{NaOH}$

Reaction of $\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right] \mathrm{Cl}_{3}$ with $\mathrm{AgNO}_{3}$