The following reaction is catalyzed by microbes of soil. The reaction belongs to which stage of Nitrogen cycle.

$2{\mathrm{NH}}_3 + 3{\mathrm{O}}_2 \to 2{{\mathrm{NO}}_2}^{-} + 2{\mathrm{H}}^{+} + 2{\mathrm{H}}_2\mathrm{O}$

• A

  Nitrification done by Nitrobacter

• B

  Nitrogen fixation by Azospirillum 

• C

  Denitrification by Pseudomonas 

• D

  Nitrification by Nitrosomonas